NEWS

ggplot2 1.0.1.9xxx
----------------------------------------------------------------

* `geom_pointrange()` gains `fatten` argument so you can control the
  size of the point relative to the size of the line.

* `stat_spoke()` is now `geom_spoke()` since I realised it's a
  reparameterisation of `geom_segment().

* Layers are now much stricter about their arguments - you will get an error
  if you've supplied an argument that isn't an aesthetic, or a parameter
  of the scale or geom. This should make it much more obvious when you have
  a spelling mistake! (#1293)

* `order` aesthetic is officially no longer supported. It never really worked,
  and was poorly documented.

* When setting limits with `coord_cartesian()`, it now applies the same
  expansion factor as setting limits with scales. You can suppress with
  `expand = FALSE` (#1207).

* `annotation_custom()` now automatically adds a unique id to each grob name,
  making it easier to plot multiple grobs with the same name (e.g. grobs of
  ggplot2 graphics) in the same plot (#1256).

* New `txhousing` dataset containing information about the Texas housing
  market. Useful for examples that need multiple time series, and for
  demonstrating model+vis methods.

* The default font size in `geom_text()` has been decreased from 5mm (14 pts)
  to 3.8 mm (11 pts) to match the new default theme sizes.

* New `stat_summary_bin()` that works like `stat_summary()` but on binned
  data. It's a generalisation of `stat_bin()` that can compute any aggregate.
  (#1274)

* It's now obvious that you can set the `binwidth` parameter for
  `stat_bin_hex()`, `stat_summary_hex()`, `stat_bin_2d()`, and
  `stat_summary_2d()`. `stat_summary_2d()` and `stat_bin_2d()` now share
  exactly the same code for determining breaks from `bins`, `binwidth`, and
  `origin`. `stat_summary_2d()` and `stat_bin_2d()` now output in tile/raster
  compatible form instead of rect form.

* For consistency with the summary functions, `stat_binhex()` and `stat_bin2d()`
  have been renamed to `stat_bin_hex()` and `stat_bin_2d()` (the existing
  functions will continue to work but will be deprecated in the future)
  (#1274).

* New `layer_data()` function extracts the data used for plotting for a given
  layer. It's mostly useful for testing.

* `facet_wrap()` gains a `dir` argument to control the direction the
  panels are wrapped in. The default is "h" for horizontal. Use "v" for
  vertical layout (#1260).

* Legends no longer inherit aesthetics if `inherit.aes` is FALSE (#1267).

* The default themes has been tweaked in various minor ways. The legend
  title and axis titles are now given the same treatment. The default
  font size has been dropped from 12 to 11. The axes labels are now
  darker.

* Sizes in ggplot2 are measured in mm. Previously they were converted to
  pts (for use in grid) by multiplying by 72 / 25.4. However, grid uses
  printer's points, not Adobe (big pts), so sizes are now multiplied by
  72.27 / 25.4.

* In legend for bars and rectangles, display border colour as border,
  rather than strikethrough.

* ggplot no longer throws an error if you your plot doesn't have any
  layers.  Instead it automatically adds `geom_blank()` (#1246)

* `geom_smooth()` is no longer so chatty. If you want to know what the deafult
  smoothing method is, look it up in the documentation! (#1247)

* `geom_smooth()`/`stat_smooth()` and `geom_quantile()`/`stat_quantile()` no
  longer pass ... on to the underlying model. Instead, put additional arguments
  in `method.args` (#1245, #1289).

* `element_text()` gains a margins argument which allows you to add additional
  margins around text elements in the plot. The default themes have been
  adjusted to add a little extra spacing between titles and text so the plots
  don't feel so cramped. The default margins scale with the theme font size,
  so the appearance at larger font sizes should be considerably improved
  (#1228). As part of these changes `axis.ticks.margin` has been deprecated:
  now use the margin property of `axis.ticks`.

* ggplot2 re-exports grid `arrow()` and `unit()` so you don't need to attach
  grid or use `grid::` for these commonly used functions (#1225)

* `geom_histogram()` and `geom_smooth()` now only inform you about the
  default values once per layer, rather than once per panel (#1220).

* `geom_bar()` and `geom_histogram()` no longer share `stat_bin()`. Now
  `geom_bar()` has its own stat, `stat_bar()`. This is useful if you want to
  display a bar chart of continuous data, drawing a bar at each unique
  location.

* `stat_summary2d()` has been renamed to `stat_summary_2d()` (with
  an alias so you can keep using the old method).

* Date and datetime scales now have `date_breaks`, `date_minor_breaks` and
  `date_labels` arguments so that you never need to use the long form
  `scales::date_breaks()` or `scales::date_format()`.

* `aes_auto()` has been deprecated. `aes_()` added as alias to old `aes_q()`.
  `aes_()` can now use formulas, so the most concise SE version of
  `aes(carat, price)` is now `aes_(~carat, ~price)`.

* New dataset `economics_long` is the economics data in long form.

* `facet_wrap()` gains a `labeller` option. (@lionel-, #25)

* The labeller API has been updated to offer more control when
  facetting over multiple factors (e.g. with formulae such as `~cyl +
  am`). Before, a labeller function would take `variable` and `value`
  arguments and return a character vector. Now, they take a data frame
  of character vectors and return a list. The input data frame has one
  column per factor facetted over. Each column in the returned list
  becomes one line in the strip label. See documentation for more
  details. Labellers offer the `multi_line` argument to control
  whether to display one or multiple lines. Furthermore, referring to
  `x` in backquoted expressions with `label_bquote()` is
  deprecated. You can now refer to the variable names
  instead. (@lionel-)

* There is a new labeller `label_context()`. Its behaviour depends on
  the number of factors facetted over. With a single factor, it
  displays only the values, just as before. But with multiple factors
  (e.g. with formulae such as `~cyl + am`), the labels are dispatched
  to `label_both()` to display both the variables and the values and
  make the plot clearer. (@lionel-)

* `show_guide` has been renamed to `show.legend`: this more accurately
  reflects what it does (control appearance in legend), and uses the same
  convention as other ggplot2 arguments (i.e. a `.` between names).

* New `cut_width()` is a convenient replacement for the verbose
  `plyr::round_any()`, with the additional benefit of offering more
  control.

* New `luv_colours` dataset which contains the locations of all
  built-in `colors()` in Luv space.

* `scale_*_gradient2()` defaults to using Lab colour space.

* `scale_fill_grey()` now uses red for missing values. This matches
  `scale_colour_grey()` and makes it obvious where missing values lie.
  Control with `na.value`.

* `geom_label()` works like `geom_text()` but draws a solid background
  behind each label (#1039).

* `stat_bindot()` has been removed because it's so tightly coupled to
  `geom_dotplot()`. If you happened to use `stat_bindot()`, just change to
  `geom_dotplot()` (#1194).

* Character labels in `facet_grid()` are no longer (incorrectly) coerced into
  factors. This caused problems with custom label functions (#1070).

* `scale_y_continuous()` now also transforms the `lower`, `middle` and `upper`
  aesthetics used by `geom_boxplot()`: this only affects
  `geom_boxplot(stat = "identity")` (#1020).

* `stat_summary()` (#1242), `stat_summary_hex()` and `stat_summary2d()` no
   longer pass `...` on to their summary functions - instead they have a new
   argument `fun.args`, a list of arguments to pass on.

* The internals of positions have been cleaned up considerably. You're unlikely
  to notice any external changes, although the documentation should be a little
  less confusing since positions now don't list parameters they never use.

* You can now suppress the appearance of an axis/legend title (and the space
  that would allocated for it) with `NULL` in the `scale_` function. To
  use the default lable, use `waiver()` (#1145).

* `geom_bin2d()` will now let you specify one dimension's breaks exactly,
  without touching the other dimension's default breaks at all (#1126).

* `labels = NULL` now works with `guide_legend()` and `guide_colorbar()`.
  (#1175, #1183).

* Improved documentation for `aes()`, `layer()` and many geoms and scales. I've
  tried to reduce the use of `...` so that you can see all the documentation in
  one place rather than having to navigate through multiple pages. Use
  of `qplot()` in examples has been minimised (#1123, @hrbrmstr). Tighly
  linked geoms and stats (e.g. `geom_boxplot()` and `stat_boxplot()`) are
  now documented in the same file so you can see all the arguments in one
  place.

* `geom_abline()`, `geom_hline()` and `geom_vline()` have been rewritten to
  have simpler behaviour and be more consistent:

    * `stat_abline()`, `stat_hline()` and `stat_vline()` have been removed:
      these were never suitable for use other than with `geom_abline()` etc
      and were not documented.

    * `geom_abline()`, `geom_vline()` and `geom_hline()` are bound to
      `stat_identity()` and `position_identity()`

    * Intercept parameters can no longer be set to a function.

    * They are all documented in one file, since they are so closely related.

* Scales no longer round data points to improve performance of colour
  palettes. Instead the scales package now uses a much faster colour
  interpolation algorithm (#1022).

* `scale_x_date()` now clips dates outside the limits in the same way as
  `scale_x_continuous()` (#1090)

* The `stat` and `position` arguments to `qplot()` have been deprecated.

* The movies dataset has been moved into its own package, ggplot2movies,
  because it was large and not terribly useful. If you've used the movies
  dataset, you'll now need to explicitly load the package with
  `library(ggplot2movies)`.

* The default legend will now allocate multiple rows (if vertical) or
  columns (if horizontal) in order to make a legend that is more likely to
  fit on the screen. You can override with the `nrow`/`ncol` arguments
  to `guide_legend()`

    ```R
    p <- ggplot(mpg, aes(displ,hwy, colour = model)) + geom_point()
    p
    p + theme(legend.position = "bottom")
    p + guides(colour = guide_legend(ncol = 1))
    ```

* `lims()` makes it easy to set the limits of any axis (#1138).

* Switched away from proto and reference class objects to ggproto. This makes it
  easier to extend ggplot2, because ggproto supports clean cross-package
  inheritance.

* `stat_function` computed the function with the transformed (not
  original data) values. This caused the computed values to be wrong
  if a different scale, other than untransformed continuous, was
  used. Function is now evaluted in original data scale
  values. (@BrianDiggs, #1011)

* Fixed segment annotations not transforming with scales (@BrianDiggs, #859)

* `geom_point()` changes the default shape from 16 to 19 - this has a
  better display on the default linux graphics device. (It's very slightly
  smaller than the old point, but it should affect any graphics significantly)

* `theme_minimal()` got slightly more minimal by removing the axis ticks:
  labels now line up beneath the grid lines (@tomschloss, #1084)

* `ggsave()` has been simplified a little to make it easier to maintain.
  It no longer checks that you're printing a ggplot2 object (so now also
  works with any grid grob) (#970), and always requires a filename.
  Parameter `device` now supports character argument to specify which supported
  device to use ('pdf', 'png', 'jpeg', etc.), for when it cannot be correctly
  inferred from the file extension (for example when a temporary filename is
  supplied server side in shiny apps) (@sebkopf, #939). It no longer opens
  a graphics device if one isn't already open - this is annoying when you're
  running from a script (#1326)

* Add access to the new `direction` argument of `scales::brewer_pal` and
  simplify changing the order of colours for `scale_*_brewer` and
  `scale_*_distiller` (@jiho, #1139)

* `facet_wrap()` more carefully checks its `nrow` and `ncol` arguments
  to ensure that they're specified correctly (@richierocks, #962)

* Improved the calculation of segments needed to draw the curve representing
  a line when plotted in polar coordinates. In some cases, the last segment
  of a multi-segment line was not drawn (@BrianDiggs, #952)

* All datasets have class `tbl_df` so if you also use dplyr, you won't
  accidentally print all the data. `economics` has been brought up to date to
  2015-04-01.

* All instances of partial matched dollar expressions were removed (@jimhester,
  #1134)

* `geom_text()` gains `nudge_x` and `nudge_y` arguments to offset labels from
  the x & y position (#1120). `check_overlap = TRUE` provides a simple
  resolution to label overplotting (#1039). `hjust` and `vjust` can now
  be character vectors: "left", "center", "right", "bottom", "middle", "top".
  New options include "inward" and "outward" which align text towards and
  away from the center of the plot respectively.

* `geom_crossbar()` sets grouping correctly so you can display multiple
  crossbars on one plot. It also makes the default `fatten` argument a little
  bigger to make the middle line more obvious (#1125).

* `guide_colorbar()` no longer fails when the legend is empty - previously
  this often masked misspecifications elsewhere in the plot (#967)

* `Geom`, `Stat` and `Position` are now exported, making it easier to create
  new geoms, stats and positions in other packages (#989).

* `facet_grid()` and `facet_wrap()` gain a `switch` argument that
  allows the facet titles to be displayed near the axes. They then act
  as axes subtitles. Can be set to "x", "y" or "both" (the latter only
  for grids) to control which label strips are switched. (@lionel-)

* New `theme_void()`, which is completely empty. Useful for plots with non
  standard coordinates or for producing numerical drawings with R. (@jiho, #976)

* New `geom_curve()` that adds curved lines, similar to `geom_segment()`.
  (@veraanadi, #1088)

* New `validate = FALSE` parameter to `theme()` makes it possible to turn off
  validation, and hence store arbitrary additional data in the themes.
  (@tdhock, #1121)

* Create correct legend for continuous color even if there is only one color
  (@krlmlr, #943)

* Position adjustments no longer warn about potentially varying ranges
  because the problem rarely occurs in practice and there are currently a
  lot of false positives since I don't understand exactly what FP criteria
  I should be testing.

* New dark-backgrounded theme, `theme_dark()`, meant to make colours pop out
  (@jiho, #1018)

* `aes_string()` now only parses character inputs. This problems bugs when
  using it with numbers and non default `OutDec` settings (#1045).

* `cut_number()` gives error message if insufficient data values to
  produce requested bins (#1046).

* `facet_wrap()` and `facet_grid()` now allow you to use non-standard
  variable names (provided that they surrounded by backticks) (#1067)

* Add `position_nudge()` for slightly off setting labels (or other geoms)
  from their corresponding points (#1109).

* All defunct functions and arguments have been removed.

* `stat_bin()` now defaults to using counts instead of proportions.
  `geom_count()` provides a convenient alias.

* `scale_size()` now maps values to _area_, not radius. Use `scale_radius()`
  if you want the old behaviour (not recommended, except perhaps for lines).

* `ggplot()` now captures the parent frame to use for evaluation,
  rather than always defaulting to the global environment. This should
  make ggplot more suitable to use in more situations (e.g. with knitr)

* Tweaked default `theme_grey()` background colour from grey90 to grey92:
  this makes the background recede into the background a little more.

* Bumped the default `size` for `geom_smooth()` up to 1. To continue to use
  the previous size, set `size = 0.5`. `geom_smooth()` gains explicit
  `method`, `se` and `formula` arguments to make it easier to see what the
  most important options are.

* `stat_bin()` gains `bins` arguments, which denotes the number of bins. Now
  you can set `bins=100` instead of `binwidth=0.5`. Note that `breaks` or
  `binwidth` will override it. (@tmshn, #1158, #102)

* `geom_histogram()` gains `binwidth`, `bins`, origin` and `right` arguments so
  you can see the most important arguments to the underlying `stat_bin()`
  computation.

* `geom_jitter()` gains `width` and `height` arguments to make it easier
  to control the amount of jittering without using the lengthy
  `position_jitter()` function (#1116)

* ggplot2 now exports `alpha()` from the scales package. This means you
  don't need to do `library(scales)` or `scales::alpha()` to access that
  handy function (#1107).

* new theme setting `panel.ontop` (logical) allows placing background elements
  (e.g., gridlines) on top of data. Usually used with blank or transparent
  `panel.background`.  (@noamross. #551)

* Add `stroke` aesthetic to `geom_point` controlling the stroke width of the
  border for shape types 21 - 25 (#1133, @SeySayux). Like `size`, the unit
  of stroke is `mm`. A point with `size = 5, stroke = 5` will be 10 mm wide.
  (#1142)

* `override.aes` now works with American aesthetic spelling, e.g. color

* Fixed `strip_dots` to work with anonymous functions within calculated
  aesthetics (e.g. `aes(sapply(..density.., function(x) mean(x))))`
  (#1154, @NikNakk)

* Automatically computed breaks do not lead to an error for transformations like
  "probit" where the inverse can map to infinity (#871, @krlmlr)

ggplot2 1.0.1
----------------------------------------------------------------

* Fixes to pass `R CMD check --run-donttest` in R-devel.

* Improvements to order of colours and legend display for continuous colour
  scales extracted from colorbrewer palettes by `scale_*_distiller()` (@jiho, 1076)

ggplot2 1.0.0
----------------------------------------------------------------

NEW FEATURES

* New coordinate system for small scale maps. `coord_quickmap()` computes and
  sets the correct aspect ratio between one degree of latitude and one degree
  of longitude at the centre of the plotted region. It does not perform full
  fledged mapping projection as `coord_map()` does and therefore is much
  faster. Yet, it gives a correct approximation for small scale maps (a few
  degrees in either direction) at medium to low latitudes (@jiho, #922).

* `geom_boxplot` gain new `varwidth` argument for controlling whether or not
  the width of boxplots should be proportional to the size of the groups
  (@tsieger, #927).

* `position_jitterdodge()` combines `position_jitter()` and `position_dodge()`,
  allowing the user to plot and align points generated by e.g. `geom_point()`
  with those generated by a dodged `geom_boxplot()`. See
  `example(position_jitterdodge)` for a potential usage. (@kevinushey, #932)

* Allow specifying only one of the limits in a scale and use the automatic
  calculation of the other limit by passing NA to to the limit function,
  `xlim()` or `ylim()` (@jimhester, #557).

* Allow to use brewer palettes for continuous scales, through the new
  `scale_fill/colour_distiller()` functions (@jiho, #925).

* `stat_ellipse()` adds data ellipses. It supports bivariate normal and t distributions,
  as well as a euclidian distance circle. (@jofrhwld, #926)

* Add new themes: `theme_linedraw()` is similar to `theme_bw()` but with
  truly only white and black elements and spacing between elements identical
  to `theme_gray`. `theme_light` is similar but with light gray box and axes
  around the plot, to emphasise content more (@jiho, #923)

* new theme settings panel.margin.x and panel.margin.y (units) allow
  specifying horizontal and vertical gap between panels in facetted plots (for
  both grid and wrap).  (Kirill Müller. Fixes #839)

* Fix vertical justification for rotated text.  This will change the appearance
  of plots that use textual elements that are rotated by 90° or 270° and have a
  `vjust` parameter other than the default 0.5; the interpretation of `vjust`
  and `hjust` is now the same for both rotated and non-rotated text elements
  (0 = top/left, 1 = bottom/right, 0.5 = centered).  (@krlmlr, #883)

* Added helper function `labeller()` for formatting faceting values.
  (@stefanedwards, #910). Added `label_wrap_gen` based on
  https://github.com/hadley/ggplot2/wiki/labeller#writing-new-labellers
  (@stefanedwards, #910)

BUG FIXES AND MINOR IMPROVEMENTS

* `aes()` no more treats variables like `a..x..b` as a calculated aesthetic.
  (@krlmlr, #834.)

* New `aes_q()` function to generate aesthetic specifications from
  quoted calls/names. `aes_string()` uses names `x` and `y` for first
  two unnamed arguments.

* `fortify.SpatialPolygonsDataFrame()` now calls `polygons` without
  requiring the `sp` to be loaded first (@seancarmody, #879).

* The outliers of `geom_boxplot()` use the default colour, size and shape from
  `geom_point()`. Changing the defaults of `geom_point()` with
  `update_geom_defaults()` will apply the same changes to the outliers of
  `geom_boxplot()`. Changing the defaults for the outliers was previously not
  possible. (@ThierryO, #757)

* `geom_dotplot()` now works with `qplot()`. (@rasmusab. Fixes #825)

* Marginal improvements to `theme_bw()` and `theme_classic()` (@jiho, #934)

* `stat_smooth()` checks for `method = "auto"` and `method = "glm"` in
  a safer way.

* Add `"none"` to documentation of `theme()` for parameter `legend.position`
  (@krlmlr, #829).

REMOVED FUNCTIONALITY

* `ggpcp()`, `ggfluctuation()`, `ggmissing()`, `ggstructure()`, and
  `ggorder()` are now defunct and have been removed.

ggplot2 0.9.3.1
----------------------------------------------------------------

BUG FIXES

* The theme element `legend.box.just` now can be set. It was not properly
  recognized before.

* `stat_density2d` previously resulted in errors when geom="polygon". This
  is fixed. (Fixes #741 and #749)

* `annotation_logticks` previously drew one set of logticks for each group,
  and inherited aesthetic mappings like colour. It no longer does this. (Fixes
  #767)

* Plots with geom_crossbar not display correct symbol in legend. (Fixes #768)

* Grouping is no longer set automatically by `stat_summary()`, allowing for
  summary paths. This reverts a change made for 0.9.3. (Fixes #732 and #739)

ggplot2 0.9.3
----------------------------------------------------------------

* The `plotmatrix` function has been deprecated and prints a warning
  message.

* `stat_bin` now produces warning messages when it is used with set or
  mapped y values. Previously, it was possible to use `stat_bin` and
  also set/map y values; if there was one y value per group, it would
  display the y values from the data, instead of the counts of cases for
  each group. This usage is deprecated and will be removed in a future
  version of ggplot2. (Winston Chang. Fixes #632)

* Several small changes were made so that ggplot2 is compatible with
  plyr <= 1.7.1 as well as plyr > 1.7.1.

* `geom_polygon` draws multiple polygons as a single grob instead of as
  separate grobs. This results in much better performance. For example,
  drawing a world map is about 12 times faster. (Winston Chang. Fixes #666)

MINOR FEATURES

* A new theme `theme_minimal` has been added. This theme is based on
  `theme_bw`, but does not have outlines around many of the rectangular
  elements. (Baptiste Auguie)

* A new theme `theme_classic` has been added. This theme has is based on
  `theme_bw`. It has x and y axis lines, but no box around the plotting area
  and no grid lines. (Thanks to David Kahle)

* `geom_segment` allows setting `lineend`. (Jean-Olivier Irisson)

* `ggsave` raises an error when making images larger than 50x50 inches.
  This prevents accidentally creating extremely large bitmap images that
  hang R and eat up memory. (Winston Chang. Fixes #517)

* `train_cartesian` and `train_trans` are no longer memoized. Previously
  the results of these functions were saved and so they would not
  respond changes in the operating environment, such as a change in
  locale. (Winston Chang. Fixes #592)

* In `stat_ydensity` and `geom_violin`, the `scale` argument now accepts
  the value "width", for equal widths. Additionally `scale="equal"` has
  been deprecated, in favor of "area". (Jean-Olivier Irisson)

* `stat_quantile` now supports `rqss`.

* `scale_size_area` has been added as a replacement for `scale_area`. This
  makes the naming more consistent. The new scale also by default makes the
  area of points proportional to the value, which is different from what
  `scale_area` does. (Fixes #635)

* Functions now have gradual deprecation behavior with the `gg_dep` function.

* Scales for required but missing aesthetics (x and y) are now automatically
  added. (Fixes #676)

* `geom_crossbar` previous raised a warning when notches were used and the
  notches went outside the hinges. This has been changed to a message.

BUG FIXES

* With `geom_segment`, when a variable mapped to `linetype` had an NA
  value, it would raise an error. This is now fixed. (Winston Chang.
  Fixes #623)

* When using `coord_map` with some projections, latitude lines wrapped
  around the globe and added extra lines. (Winston Chang. Fixes #562)

* `stat_summary` now calculates a unique value at each x. (Winston
  Chang. Fixes #622)

* Colorbar guides now supports language objects returned from functions
  like `math_format()`, and will render them as expressions. (Kohske
  Takahashi)

* When using `coord_polar`, NA or NaN values caused errors. They are now
  ignored instead. (Winston Chang)

* Text theme elements used in `guide_legend`, such as `label.theme`, caused
  confusing errors when the angle wasn't set. Now it produces a more
  informative error message.

* Theme elements now have their subclass listed first, before the `element`
  class. (Thanks to Jeffrey Arnold)

* Previously when free scales were used with non-cartesian coords, they just
  wouldn't work. Now ggplot throws an error with an informative message.
  (Fixes #673)

* `geom_dotplot` previously worked with `position="dodge", but did not work
  when using `position=position_dodge()`. It now works with both. (Fixes
  #709)

* For linetype scales, NA values previously caused errors. Now `na.value`
  for linetype scales defaults to "blank". (Fixes #711)

ggplot2 0.9.2.1
----------------------------------------------------------------

BUG FIXES

* find_global now searches for objects in the namespace environment
  instead of the package environment. This fixes problems when ggplot2
  is imported to another package but not attached.

ggplot2 0.9.2
----------------------------------------------------------------

THEME SYSTEM

* The theme system has been completely rewritten. (Winston Chang)

* The functions `theme_text`, `theme_line`, and so on have been renamed to
  `element_text`, `element_line`, and so on.

* The `opts()` function has been renamed to `theme()`.

* To set the plot title, use `labs(title = "...")` or `ggtitle("...")
  instead of `opts(title = "...")`.

* Elements are now just lists of properties, instead of functions that
  return grobs.

* Theme elements now can inherit properties. For example, `axis.title.x`
  inherits properties from `axis.title`, which in turn inherits from
  `text`. The inheritance tree is stored in ggplot2::.element_tree.

* Theme objects can now be added to each other with `+`, without a ggplot
  object. There is also a new `%replace%` operator for adding theme
  objects together.

* Vertical and horizontal grid lines can now be controlled independently,
  with `axis.grid.major.x`, `axis.grid.major.y` (and the same for minor);
  `axis.ticks.x` and `axis.ticks.y`; and `axis.line.x` and `axis.line.y`.

* The `size` property of theme elements can be defined relative to the
  parent objects, using the `rel()` function.

MINOR FEATURES

* ggplot2 now uses the external gtable package instead of internal gtable
  functions.

* The condition that set parameters (e.g. `colour = "red"`) could only be of
  length one has been relaxed - they may now be of length one, or exactly the
  same length as the data. Recycling is not done because it makes it harder to
  spot problems. This makes `annotate` considerably more flexible. (Fixes
  #489)

* `stat_contour` is now somewhat faster

* new stat class `stat_ecdf` that shows empirical cumulative distribution
  function. (Kohske Takahashi)

* Dependency on `gpclib` removed, and `fortify.SpatialPolygonsDataFrame` will
  now use `rgeos` if available - this is particularly useful if you're not
  able to use the non-free `gpclib`.

* `ggsave` now supports emf output files.

* all "template" plots (`plotmatrix`, `ggorder` etc) have been deprecated and
  will be removed in a future version. These plots are poorly tested and
  poorly supported and really belong in a separate package.

* The default guide for continuous color/fill scale is now colourbar.
  (Kohske Takahashi. Fixes #555)

* The arrowhead of geom-path and geom-segment with `arrow = TRUE` is
  now filled with the same colour as the path.

* The algorithm for calculating breaks locations has been changed from
  `pretty_breaks()` to `extended_breaks()` from the 'labeling' package
  by Justin Talbot. (Winston Chang. Fixes #580)

* `scale_type`, the function used to pick which type of scale should be
   used for a given type of input variable is now an S3 generic. That
   means that if you want to add a new default type of scale you can
   provide a method - it should return a string giving the name of the
   scale to use (e.g. "continuous", "discrete", "date")

* When there are multiple guides (legends), the order that they are
  displayed can now be controlled manually. (Kohske Takahashi. Fixes
  #470)

* When a scale for a given aesthetic is added to a plot more than once,
  display a message indicating that the first scale will be replaced.
  (Winston Chang. Fixes #518)

DOCUMENTATION

* All geoms and stats now document their aesthetics. (Thanks to joranE.
  Fixes #447)

BUG FIXES

* `scale_x_continuous` now respects `na.value` (Fixes #522)

* `geom_map` now correctly uses set aesthetics (e.g. `colour = "green"`)

* Setting breaks outside the limits of the x or y axis no longer causes
  errors. (Kohske Takahashi. Fixes #552)

* `facet_locate` no longer evaluates unneeded expressions. (Winston
  Chang. Fixes #565)

* `annotation_map` now gets group id from munched data. (Winston Chang.
  Fixes #568)

* `geom_raster` now supports alpha. (Kohske Takahashi. Fixes #596)

* Both axis lines are now drawn above the plotting area panel.
  (Winston Chang. Fixes #585)

* The jitter resolution is now correctly calculated when the data
  does _not_ include zero. (Thanks to Karl Ove Hufthammer. Fixes #572)

* Legend icons for `geom_boxplot` now display linetype. (Kohske
  Takahashi. Fixes #608)

* Facets now appear in the correct order when layers with different
  factor levels are added. (Winston Chang. Fixes #543)

* Distances in polar coordinates are calculated along spiral arcs,
  instead of straight-line distance. (Winston Chang. Fixes #471)

* `fortify.SpatialPolygonsDataFrame` now uses the correct ordering.
  (Charlotte Wickham. Fixes #434)

* `stat_vline` and `stat_hline` no longer throw errors when
  `xintercept` and `yintercept` are passed to them. (Winston Chang.
  Fixes #624)

ggplot2 0.9.1
----------------------------------------------------------------

MINOR FEATURES

* `ggstructure` and `ggorder`, which call `ggpcp`, no longer have a
  `scale` argument since `ggpcp` does not have one.

* built in datasets have been checked to make sure they use characters,
  factors and ordered factors appropriately

* `geom_raster` and `annotation_raster` gain new `interpolate` argument for
  controlling whether or not rasters are interpolated

* Added `plot` as an alias for `print` for ggplot objects.

* Visual tests have been moved to /visual_test and modified to work with the
  vtest package. (Thanks to Winston Chang)

* `geom_dotplot`: now supports stacking. It uses `stackgroups = TRUE` instead
  of the usual position="stack", for technical reasons. It also will stack in
  the x direction when binning along the y axis. (Thanks to Winston Chang)

* `geom_rug` now allows control over which sides to put the rug lines, with
  the `sides` argument. (Thanks to Winston Chang)

* `annotation_logticks`: a new geom that adds tick marks on the inside of the
  plotting rectangle that have diminishing spacing for log-10 axes. (Thanks
  to Winston Chang)

* Coordinate expansion is now handled by an interaction of the scale and
  coord, rather than by the scale only. Also, the `wise` argument is no
  longer needed. (Thanks to Winston Chang and Kohske Takahashi)

BUG FIXES

* `facet_grid` no longer drops duplicate cases (Fixes #443)

* `munch_range` properly reports the x and y range. (Thanks to Winston Chang)

* `stat_bin2d` handles data with NA in the position variables. Error was
  triggered when scale was limited to a range smaller than the range of
  the data. (Bug reported by Tao Gao; diagnosed and fixed by Brian Diggs)

* `scale_*_identity` will now produce a legend when `guide = "legend"` and no
  breaks or labels are supplied (Fixes #453)

* `geom_map` now works with `coord_map` (Fixes #480)

* discrete scales now accept named vectors of labels again (Fixes #427)

* `geom_raster` works better with categorical input (Fixes #463)

* `qplot` no longer uses non-standard evaluation for geom/stat arguments - it
  doesn't seem to be needed and was causing problems when qplot was used in
  special environments (e.g. in knitr) (Fixes #377)

* `coord_train.polar` and `coord_train.trans` remove NAs from breaks.
  (Thanks to Winston Chang. Fixes #422)

* Theta breaks with `coord_polar` have equal angular spacing. (Thanks to
  Winston Chang and Kohske Takahashi. Fixes #288)

* Empty data frames are now handled correctly: layers with empty data are
  dropped silently, instead of inheriting data from the plot. (Thanks to
  Winston Chang. Fixes #31, #332, #506 and #507)

* The alpha value of set colours is now preserved by default. To return to the
  old behaviour, set `alpha = 1`. (Fixes #475)

* `scale_*_manual` will throw an error if you have too few values. (Fixes
  #512)

* `facet_wrap` gets the `as.table` argument back. (Fixes #497)

* `resolution` now returns 1 when range is zero. (Fixes #526)

* Titles are displayed above legend when legend is on top. (Thanks to
  Kohske Takahashi. Fixes #432)

* Specifying breaks outside coord limits works. (Thanks to Kohske Takahashi.
  Fixes #430)

* `renames_aes` now uses exact matching instead of partial matching. (Thanks
  to Winston Chang. Fixes #529)

* `labs()` now works with American spellings. (Thanks to Winston Chang.
  Fixes #521)

* `stat_density2d` sets the limits for `kde2d` from the limits of the x and
  y scales. (Thanks to Winston Chang)

ggplot2 0.9.0
----------------------------------------------------------------

NEW FEATURES

* `annotation_custom`: a new geom intended for use as static annnotations that
  are the same in every panel. Can be used to add inset plots, tables, and
  other grid-based decorations inside the plot area (Contributed by Baptiste
  Auguié).

* `geom_map`: a new special case of `geom_polygon` useful when you are drawing
  maps, particularly choropleth maps. It is matched with `annotation_map`, an
  even faster special case when you want the same map drawn in each panel.

* `geom_raster` is a special case of `geom_tile` for equally sized rectangular
  tiles. It uses the raster functionality of R graphics devices for massively
  increased speed and much decreased file sizes. It is matched with
  `annotation_raster`, an even faster special case, for when you want to draw
  the same raster in each panel.

* `geom_violin`: an implementation of violin plots, which are a way of
  visualizing kernel density estimates. (Thanks to Winston Chang)

* `geom_dotplot`: dot plots, as described in Wilkinson (1999). To bin the
  data, it uses `stat_bindot` to bin the data, which has two methods: histodot
  and dot-density. Histodot binning uses fixed-width bins just like
  `stat_bin`, while dot-density binning uses variable-width bins. A new grob,
  `grob_dotstack` is used to render the dots. (Thanks to Winston Chang)

* New fortify methods have been added for objects produced by the `multcomp`
  package.

* `stat_summary2d` and `stat_summary_hex`. These are work like `stat_bin2d`
  and stat_binhex but allow any summarisation function (instead of just
  count). They are 2d analogs of `stat_summary`

* `facet_grid`: The space argument now supports `free_x` and `free_y` next to
  `free` and `fixed, this allows the user to adjust the spatial scaling of the
  facets in either the x or y direction. This is especially useful when the
  scales are very different. In this case space = `free` could make some
  facets very small. (Thanks to Willem Ligtenberg)

DOCUMENTATION

* Thorough clean up and checking, including documenting all arguments, adding
  systematic cross-references, and adding commonly requested examples. Thanks
  to Jake Russ and Dennis Murphy for the help.

* Complete series of aesthetics pages (grouped subsets of aesthetics) with
  examples of how to use the major ones, see e.g. `?fill`, `?shape`, `?x`,

* Added a complete list of theme opts with usage examples in `?opts`

* Added "translate" pages to demonstrate usage between qplot and ggplot, GPL,
  base and lattice graphics: `?translate_qplot_base`, `?translate_qplot_gpl`,
  `?translate_qplot_lattice`, `?translate_qplot_ggplot`,

SCALES

* Scales have been rewritten to use the new `scales` package, which does a
  much better job at defining what a scale is and making it easier for you to
  create your own scales. Scales should now behave much more consistently, and
  it should be easier for me to add new features in the future.

* `breaks` parameter can now be a function, which will be passed the scale
  limits and expected to return a character vector of breaks

* `labels` parameter can now be a function - this replaces the previous
  formatter function that only some scales possessed, and the `major` argument
  to the data time scales. This function should take a vector of breaks as
  input, and return a character vector or list of expressions as output. See
  `comma_format`, `dollar_format`, `percent_format`, `scientific_format`,
  `parse_format` and `math_format` for examples

* Transformations are now provided by the scales package - see `?trans_new`
  for list of available transformations, and how to create your own. The
  transformations in this package should do a better job at computing default
  breaks.

* Transformations for continuous scales are now detected automatically when
  the default scales are added. This ensures that dates and date times will
  display correctly when used for any aesthetic - previously they only worked
  with position scales. The system is now also easier to extend to new types
  of continuous data that you might want to plot.  (Fixes #48)

* All scales now accept a `na.value` parameter which provides an aesthetic
  value to be used for `NA` values in the data. Colour/fill scales default to
  grey, which should stand out as different from non-missing values.

* The new `oob` (out of bounds) parameter controls how scales deals with
  values outside the limits. The default action is `censor` - see `clip` for
  another option.

* Only `scale_x_log10`, `scale_x_sqrt` and `scale_x_reverse` provided as
  convenience functions for x and y scales. Use e.g. `scale_x_continuous(trans
  = "log")` to access others

* `set_default_scale` has been removed. If you want to change the default
  scale for an aesthetic, just create a function called
  `scale_aesthetic_continuous` or `scale_aesthetic_discrete` that returns the
  scale that you want.  For example:

      p <- qplot(mpg, wt, data = mtcars, colour = factor(cyl))
      p
      scale_colour_discrete <- scale_colour_brewer
      p

* Scales now automatically shrink to what is actually displayed on the plot,
  not the underlying data used for statistical transformation. If you want the
  old behaviour, supply `shrink = FALSE` to the facetting specification.
  (Fixes #125)

* `scale_colour_gradient` and `scale_fill_gradient` now use a colour scheme
  with constant hue but varying chroma and luminance. This is better because
  it creates a natural ordering inline with the order of the colour values.

FACETS

* Converted from proto to S3 objects, and class methods (somewhat) documented
  in `facet.r`. This should make it easier to develop new types of facetting
  specifications.

* The new `facet_null` specification is applied in the default case of no
  faceting. This special case is implemented more efficiently and results in
  substantial performance improvements for non-facetted plots.

* Facetting variables will no longer interfere with aesthetic mappings -
  `facet_wrap(~ colour)` will no longer affect the colour of points.

DEVELOPMENT

* ggplot2 has moved away from the two (!!) homegrown documentation systems
  that it previously relied on, and now uses roxygen extensively. The current
  downside is that this means that ggplot2 website can no longer be updated,
  but I hope work with the `helpr` package will resolve that shortly.

* ggplot2 now uses a `NAMESPACE`, and only exports functions that should be
  user visible - this should make it play considerably more nicely with other
  packages in the R ecosystem. Note that this means you now need to explicitly
  load `plyr` (and other packages) if you are using them elsewhere in your
  code.

* ggplot2 now has a start on a set of automated tests. As this test suite
  expands it will help me ensure that bugs stay fixed, and that old bugs don't
  come back in new versions. A test suite also gives me more confidence when
  I'm modifying code, which should help with general code quality.

COORDS

* Converted from proto to S3 objects, and class methods (somewhat) documented
  in `coord.r`. This should make it easier to develop new types of coordinate
  systems.

* Added a new method `coord_range` for finding the x and y range even after
  coordinates have been transformed to other names (eg., theta and r). (Thanks
  to Winston Chang)

RENDERING

* When printing a ggplot2 object, the rendered plot information is returned
  invisibly. You can capture this with (e.g.) `x <- print(qplot(mpg, wt, data
  = mtcars))` and in the future will be able to use it to get information
  about the plot computations, such as the range of all the scales, and the
  exact data that is plotted.

* Drawing a plot takes place in three documented steps: `ggplot_build` which
  creates a list of data frames ready for rendering builds, `ggplot_gtable`
  which creates a `gtable` of grobs, and `grid.draw` which renders the grobs
  on screen. Each of these returns a data structure which should be useful for
  understanding and modifying the rendered plot. This is still a work in
  progress, so please ask questions if anything is confusing.

* The `drop` and `keep` parameters to `ggsave` and `print.ggplot` have been
  dropped, as the data structure returned by `ggplot_gtable` is sufficiently
  rich enough to remove the need for them.

* Axis labels are now centred underneath the panels (not the whole plot), and
  stick close to the panels regardless of the aspect ratio.

GUIDES

* Guides (particularly legends) have been rewritten by Kohske Takahashi to
  provide considerably more layout flexibility.

* `guide_legend` now supports multi-row/column legend and reversed order,
  gives more flexible positioning of title and label, and can override
  aesthetics settings. This is useful, for example, when alpha value in a
  panel is very low but you want to show vivid legend.

* `guide_colorbar` is a guide specially for continuous colour scales as
  produced by colour and fill scales.

MINOR CHANGES

* `geom_text` now supports `fontfamily`, `fontface`, and `lineheight`
  aesthetics for finer control over text display. (Thanks to Kohske Takahashi
  for the patch. Fixes #60)

* `collide`, which powers `position_dodge` and `position_stack`, now does not
  error on single x values (Thanks to Brian Diggs for a fix. #157)

* `...` in `ggplot` now passed on to `fortify` method when used with an object
  other than a data frame

* `geom_boxplot`: outlier colour and shape now default to values set by the
  aesthetic mapping (thanks to suggestion by Ben Bolker), the width of the
  median line is now `fatten` times the width of the other lines (thanks to
  suggestion by Di Cook), and the line type can now be set. Notched box
  plots are now supported by setting `notch = TRUE` (thanks to Winston Chang
  for the patch).

* `ggsave` can work with cm and mm `units` (Thanks to patch from Jean-Olivier
  Irisson)

* `scale_shape` finally returns an error when you try and use it with a
  continuous variable

* `stat_contour` no longer errors if all breaks outside z range (fixes #195).

* `geom_text` remove rows with missing values with warning (fixes #191)

* New generic function `autoplot` for the creation of complete plots
  specific to a given data structure. Default implementation throws
  an error. It is designed to have implementations provided by other
  packages.  (Thanks to suggestion by Brian Diggs)

* `ggpcp` loses the `scale` argument because it relied on reshape(1) code

* `map_data` passes `...` on to `maps::map` (Fixes #223)

* `coord_fixed` accepts `xlim` and `ylim` parameters to zoom in on x and y
  scales (Fixes #91)

* ggplot2 will occasionally display a useful hint or tip on startup.  Use
  `suppressPackageStartupMessages` to eliminate

* `stat_binhex` uses correct bin width for computing y axis bounds. (Fixes
  #299, thanks to Dave Henderson for bug report and fix.)

* `stat_smooth` now adjusts confidence intervals from `loess` using a
  t-based approximation

* `stat_smooth` reports what method is used when method is "auto". It also
  picks the method based on the size of the largest group, not individually by
  group. (Thanks to Winston Chang)

* `stat_bin` and `geom_histogram` now use right-open, left-closed intervals by
  default. Use `right = TRUE` to return to previous behaviour.

* `geom_vline`, `geom_hline`, and `geom_abline` now work with non-Cartesian
  coordinate systems. (Thanks to Winston Chang)

ggplot2 0.8.9
----------------------------------------------------------------

A big thanks to Koshke Takahashi, who supplied the majority of improvements
in this release!

GUIDE IMPROVEMENTS

* key size: can specify width and height separately

* axis: can partially handle text rotation (issue #149)

* legend: now can specify the direction of element by opts(legend.direction =
  "vertical") or opts(legend.direction = "horizontal"), and legend box is
  center aligned if horizontal

* legend: now can override the alignment of legend box by
  opts(legend.box = "vertical") or opts(legend.box = "horizontal")

* legend: now can override legend title alignment with opts(legend.title.align
  = 0) or opts(legend.title.align = 1)

* legend: can override legend text alignment with opts(legend.text.align = 0)
  or opts(legend.text.align = 1)

BUG FIXES

* theme_*: can specify font-family for all text elements other than geom_text

* facet_grid: fixed hirozontal spacing when nrow of horizontal strip >= 2

* facet_grid: now can manually specify the relative size of each row and column

* is.zero: now correctly works

* +: adding NULL to a plot returns the plot (idempotent under addition)
  (thanks to suggestion by Matthew O'Meara)

* +: meaningful error message if + doesn't know how to deal with an object
  type

* coord_cartesian and coord_flip: now can wisely zoom when wise = TRUE

* coord_polar: fix point division bugs

* facet_grid: now labels in facet_grid are correctly aligned when the number
  of factors is more then one (fixes #87 and #65)

* geom_hex: now correctly applies alpha to fill colour not outline colour
  (thanks to bug report from Ian Fellows)

* geom_polygon: specifying linetype now works (thanks to fix from Kohske
  Takahashi)

* hcl: can now set c and l, and preserves names (thanks to suggestion by
  Richard Cotton)

* mean_se: a new summary function to work with stat_summary that calculates
  mean and one standard error on either side (thanks to contribution from
  Kohske Takahashi)

* pos_stack: now works with NAs in x

* scale_alpha: setting limits to a range inside the data now works (thanks to
  report by Dr Proteome)

* scale_colour_continuous: works correctly with single continuous value (fixes
  #73)

* scale_identity: now show legends (fix #119)

* stat_function: now works without y values

* stat_smooth: draw line if only 2 unique x values, not three as previously

* guides: fixed #126

* stat_smooth: once again works if n > 1000 and SE = F (thanks to bug report
  from Theiry Onkelinx and fix from Kohske Takahashi)

* stat_smooth: works with locfit (fix #129)

* theme_text handles alignment better when angle = 90

ggplot2 0.8.8
----------------------------------------------------------------

Bug fixes:

* coord_equal finally works as expected (thanks to continued prompting from
  Jean-Olivier Irisson)

* coord_equal renamed to coord_fixed to better represent capabilities

* coord_polar and coord_polar: new munching system that uses distances (as
  defined by the coordinate system) to figure out how many pieces each segment
  should be broken in to (thanks to prompting from Jean-Olivier Irisson)

* fix ordering bug in facet_wrap (thanks to bug report by Frank Davenport)

* geom_errorh correctly responds to height parameter outside of aes

* geom_hline and geom_vline will not impact legend when used for fixed
  intercepts

* geom_hline/geom_vline: intercept values not set quite correctly which
  caused a problem in conjunction with transformed scales (reported by Seth
  Finnegan)

* geom_line: can now stack lines again with position = "stack" (fixes #74)

* geom_segment: arrows now preserved in non-Cartesian coordinate system (fixes
  #117)

* geom_smooth now deals with missing values in the same way as geom_line
  (thanks to patch from Karsten Loesing)

* guides: check all axis labels for expressions (reported by Benji Oswald)

* guides: extra 0.5 line margin around legend (fixes #71)

* guides: non-left legend positions now work once more (thanks to patch from
  Karsten Loesing)

* label_bquote works with more expressions (factors now cast to characters,
  thanks to Baptiste Auguie for bug report)

* scale_color: add missing US spellings

* stat: panels with no non-missing values trigged errors with some statistics.
  (reported by Giovanni Dall'Olio)

* stat: statistics now also respect layer parameter inherit.aes (thanks to bug
  report by Lorenzo Isella and investigation by Brian Diggs)

* stat_bin no longer drops 0-count bins by default

* stat_bin: fix small bug when dealing with single bin with NA position
  (reported by John Rauser)

* stat_binhex: uses range of data from scales when computing binwidth so hexes
  are the same size in all facets (thanks to Nicholas Lewin-Koh for the bug
  report)

* stat_qq has new dparam parameter for specifying distribution parameters
  (thanks to Yunfeng Zhang for the bug report)

* stat_smooth now uses built-in confidence interval (with small sample
  correction) for linear models (thanks to suggestion by Ian Fellows)

* stat_spoke: correctly calculate stat_spoke (cos and sin were flipped, thanks
  to Jean-Olivier Irisson for bug report and fix)

ggplot2 0.8.7
----------------------------------------------------------------

* coord_map gains xlim and ylim arguments to control region of projection

* corrected label generation for computed aesthetics (..x..) and special
  names (`x x`)

* fullseq: now always returns vector of length two, even when range is 0

* geom_point legend takes more care to ensure that fill colours will be shown

* legend: fixed scale merging bug when labels were set manually

* scale_area: gains a legend argument like all other scales

* scale_colour_brewer: gains na.colour argument to set colour of missing
  values

* stat_bin2d: fix typo in breaks calculation

* stat_bin: deals with floating point rounding issues using the same
  algorithm as base::hist

* stat_density2d: fixed bug when contour = FALSE (Thanks to Takahashi Kohske)


ggplot2 0.8.6
----------------------------------------------------------------

NEW FEATURES

* trans_log1p: new log + 1 transformer contributed by Jean-Olivier Irisson

BUG FIXES

* aesthetics: fixed bug when overriding aesthetics with NULL

* annotate: adds layers with legend = FALSE

* coord_equal: correctly place tick marks (Fixes #61)

* documentation: usage statements should now be spread over multiple lines

* fortify.SpatialPolygonsDataFrame: fixed bug when region variable had missing values

* legend: don't try and display legend when unnecessary scale added

* legend: text labels now correctly left-aligned when non-numeric

* order aesthetic now correctly affects position adjustments  (Fixes #70)

* qplot loads facetting variables from global environment more correctly

* scale_date and scale_date_time now work with infinite positions

* scale_date and scale_date_time now take expand argument

* scales were not getting automatically added in many situations (Fixes #69)

* scale_manual was not returning labels in the correct format and so legends
  were not getting merged correctly

* stat_contour: fix error if x or y coordinates were negative

* stat_bin: now copes with bars of zero height (Fixes #72)

* stat_qq: always use sorted data (rather than interpolated quantiles) on
  sample axis.  This makes it behave more like qqnorm

* stat_quantile: correctly group results

* xlim now works with datetimes

* all plyr functions prefixed with their namespace to avoid clashes with other
  packages (thanks to Steve Lianoglou)


ggplot2 0.8.5
----------------------------------------------------------------

NEW FEATURES

* geom_text gains parse argument which makes it possible to display
  expressions. (Implements #50)

* all scales now have legend parameter, which defaults to TRUE. Setting to
  false will prevent that scale from contributing to the legend (Implements
  #27)

* default axis labels and legend titles are now stored in the options, instead
  of in each scale. This fixes a long standing bug where it was not easy to
  set the label for computed variable, such as the y axis on a histogram.
  Additionally, it means default scales are only added to the plot until just
  prior to plotting, instead of the previous behaviour where scales where
  added as layers were added - this could cause problems if you later modified
  the underlying data. (Implements #28)

* coord_equal: when ratio = NULL (the default), it will adjust the aspect
  ratio of the plot, rather than trying to extend the shortest axis.

* x and y positions can be set to Inf or -Inf to refer to the top/right and
  bottom/left extents of the panel. (Implements #18)

* expand_limits(): a new function to make it easy to force the inclusion of
  any set of values in the limits of any aesthetic.

NEW FEATURES (MINOR)

* aesthetics: when _setting_ an aesthetic, you may only set it to a single
  value.  This was always a good idea, but now it is enforced with an
  informative error message.

* stat_contour bump up default number of contours

* stat_density2d: make number of grid points used for density estimation
  user controllable (implements #9)

* geom_bin now allows you to set whether bins used intervals of the form
  (a, b] or [a, b) with the "right" parameter (implements #20)

* geom_path: linejoin, lineend and linemitre are now user controllable
  (implements #24)

* scales: all scales check that breaks are supplied if labels are, and
  that breaks and labels are the same length (implements #40)

* scales: if breaks are a named vector, the names will be used as labels
  (thanks to suggestion by David Kahle)

* scale_colour_gradient, scale_colour_gradient2 & scale_colour_gradientn now
  have formatter argument to match scale_continuous

* updated citation to refer to the ggplot2 book

BUG FIXES

* coord_cartesian now correctly sets limits when one or both of the position
  scales are non-linear.  (fixes #17)

* coord_equal: now works with non-linear scales (fixes #13)

* coord_map sets aspect ratio correctly (fixes #4)

* coord_polar correctly combines labels on end of axis if expressions
  (fixes #39)

* coord_trans now respects scale expand parameter (expansion occurs after
  transformation) (fixes #14)

* facet_grid with scales = "free" and space = "free" now calculates space
  correctly if the range of the scale is < 1 (fixes #1)

* facet_grid works once more when facetting with multiple variables in one
  direction (fixes #11)

* facet_wrap now sets aspect ratio correctly

* facet_wrap now maintains original order of data

* geom_hline and geom_vline now work with coord_flip (fixes #30)

* geom_path drops missing values at start and end of each line (fixes #41)

* scale_shape_discrete, scale_size_continuous, scale_alpha and
  scale_linetype_discrete added to scales to match naming convention of all
  other scales (fixes #47)

* legends now correctly calculate label widths (fixes #38)

* legends will only merge if both the title and all labels are the same.
  (fixes #16)

* legends: fix for bug #19: Legend with three constraints doesn't work

* stat_contour & stat_density2d: fix grouping bugs (issue #7)

* xlim, ylim: fix bug when setting limits of discrete scales


ggplot2 0.8.4
----------------------------------------------------------------

* aes and aes_string both convert prefixes to full names
* aesthetics: corrected list of aesthetics to include american spelling of
  colour as well as base R abbreviations
* aesthetics: fix bug in detecting which aesthetics are calculated
* aes_string treats NULL as "NULL"
* annotate now works with missing x and y (e.g. for geom_rect)
* continuous scale limits now automatically sorted
* coord_polar: fix bug if breaks not all inside limits
* facet_wrap: can now specify both ncol and nrow without getting an error
* facet_wrap: now works with statistics that produce both x and y values (e.g.
  stat_qq)
* fullseq now adds additional break on bottom if necessary, so that the
  include.lowest argument in cut never comes into play (this the source of a
  potential bug in histograms)
* geom_boxplot: alpha now affects fill colour of boxes only
* geom_path correctly switches to segments if varying alpha used (thanks to
  Karl Ove Hufthammer for the report and Baptiste Auguie for the fix)
* geom_point: the alpha aesthetic now also affects the fill.
* geom_ribbon always sorts input to avoid problems with certain pathological
  inputs
* geom_smooth was incorrectly applying alpha to line colour in the legend
* nullGrob renamed to zeroGrob to avoid name conflict with grid
* position_collide now works with missing values
* position_stack: fixed bug in detection of overlap for negative values
* scale_discrete_position now uses drop argument to force dropping of unused
  levels
* scale_gradient, scale_gradient2 and scale_gradientn now uses label
  parameters, if supplied
* scale_x_inverse, scale_y_inverse now actually work, and added recip as alias
* stat_qq now correctly groups results
* stat_smooth will not try and fit a line to 2 or fewer points (previously
  didn't try for only 1 point)
* stat_spoke now works with reversed scales
* grouping: now consistent between different geoms (Issue #33)

ggplot2 0.8.3
----------------------------------------------------------------

New features

* alpha: new aesthetic, with scale alpha.  Where a geom has both fill and colour, alpha affects the fill.

* annotate: new annotate function to make it easier to add annotations to plots

* facet_grid now takes strip label function from parameter labeller, not theme setting

* facet_grid: gains as.table argument to control direction of horizontal facets

* fortify: full set of methods for turning data from the sp package into data frames that can be plotted with ggplot2

* geom_errorbarh: new geom for horizontal error bars

* labels_parsed and labels_bquote functions to make it easier to display expressions on facet labels

* scale_manual now supports breaks and limits

* subset: experimental new feature.  Layers now have a subset argument, which takes subsets formatted like .(var1 < 5, var2 == 3) etc.

* xlim and ylim now work recognise Date and POSIXct classes to create date and date_time scales respectively

Dealing with missing values

* facet_wrap: add drop argument to control whether or not panels for non-existent combinations of facetting variables should be dropped or not.  Defaults to TRUE

* scale_discrete: empty factor levels will be preserved, unless drop = TRUE

Bug fixes

* added presidents dataset from book to package

* American spelling of color accepted in as geom parameter, and all colour
  scales have alias spelled color (e.g. scale_color_hue)

* facet_wrap: contents guaranteed to be clipped to panel

* facet_wrap: corrected labelling when facetting by multiple variables (thank
  to Charlotte Wickham for a clear test case)

* geom_histogram now works with negative weights (provided position =
  "identity").  This is useful for creating back to back histograms.

* geom_step: improve legend

* geom_text: better legend

* geom_vline, geom_hline, geom_abline: should work in yet more situations

* resolution: fixed bug in computation of resolution that lead to (e.g.)
  incorrect boxplot widths when there was only a single x value in a group.

* position_stack: fixed bug in detection of overlap for very large bins

* scale_discrete: factor levels no longer mistakenly reordered

* scale_hue: now spans full range of hue if it less than 360 degrees

* scale_hue: rotated default hue range by 15 degrees to avoid unfortunate
  red-green contrast in two colour case

* show now works with ggplot objects

* stat_sum: fixed bug which resulted in dropped aesthetics

* stat_summary: now warns when dropping records with missing values

* stat_summary: should be a little faster

* stat_summary: correctly passes ... arguments on fun.data

* theme_bw: corrected justification of axis.text.y

* trans: bug fixes to logistic transformation

* order aesthetic should work again

ggplot2 0.8.2
----------------------------------------------------------------

New features

* borders, fortify.map and map_data to make it easier to draw map borders and
  choropleth maps

* cut_interval and cut_number utility functions to discretise continuous
  variables

* stat_summary has reparameterised to make it easier to specify different
  summary functions.  It now has four parameters: fun.y, fun.ymin and
  fun.ymax; and fun.data.  See the documentation for stat_summary for more
  details

Minor improvements

* ggfluctuation: default to aspect ratio that produces squares

* ggsave: filename now first parameter, not second

* qplot: if sample aesthetic is used, stat automatically set to qq

* scale_datetime: improved breaks calculation

* scale_gradient: better default colour scheme from red to blue (thanks to
  Charlotte Wickham for providing the Munsell colours)

* scale_size and scale_area: increased default size range

* stats: all give useful error message if missing a required aesthetic

* theme_set warns if missing needed theme elements

* theme_text: now possible to right and left align text with hjust=0 and hjust=1 respectively

Bug fixes

* be explicit about is.discrete to avoid clash with Hmisc

* facet_wrap: work around R bug so no longer crashers when ncol = 1

* geom_errorbar now works correctly with dashed lines

* geom_path will now silently ignore lines with less than 2 points (instead of
  throwing a mysterious error as before)

* geom_path now responds to the size aesthetic once more

* geom_polygon etc now correctly displays linetype on legends

* geom_step now works with multiple groups

* geom_vline and geom_hline: fix bug when mapping intercept to variable in
  data frame

* ggsave: path parameter correctly sets path

* guides: fix broken legend from default stat aesthetics (e.g. for stat_sum)

* scale_manual now works better with missing values

* scale_manual: labels now correctly sets legend labels.

* stat_density_2d: no longer passes unnecessary parameters to kde2d causing an
  error message (seen when setting aesthetics with qplot)

* stat_pointrange: better relationship between point and line widths

* stat_sum now correctly preserves other aesthetic columns (should be a bit faster too)


ggplot2 0.8.1
----------------------------------------------------------------

New features

* new labs, xlab & ylab functions for easily modifying axis labels and legend titles

* qplot now guesses what geom you want based on the position aesthetics that you provide:

  * both x & y: scatterplot

  * only x: histogram

  * only y: scatterplot of seq_along(y) vs y

* scale_datetime: a first attempt at a scale for date time objects of class POSIXt

Aesthetic improvements

* legends should now work in cases where you have multiple layers the use the
  same geom and have different aesthetic mappings

* theme: new theme setting legend.key.size determines size of keys in legend

* theme: new theme setting plot.margins to control the plot margins

* tweaks to plot and legend layout

Other minor improvements

* geom_point warns if missing values present in data and not displayed on plot

* geom_smooth gives a more accurate warning when you have incorrectly specified the grouping

* geom_smooth will switch to an alternative smoothing method (mgcv::gam(y ~
  s(x, bs = "cr"))), when there are more than 1000 observations

* layers gain a legend argument, which allow you to force the layer either
  into (TRUE) or out of (FALSE) the legend

Bug fixes

* coord_equal now calculates scales correctly again

* coord_flip: flips axes labels again too

* coord_trans fix bug where transformation incorrect

* facet_grid: fix bug where tick labels where being produced outside the range of the axes

* facet_wrap: fixed bug with ncol = 1 or nrow = 1

* facet_wrap: labels correctly clipped to axis ranges

* facet_wrap: labels will match panels even when factor levels are not in alphabetical order

* facet_wrap: now works when a layer doesn't contain every level of the faceting variables

* geom_abline should now work in a wider variety of situations

* geom_smooth now gives correct asymmetric standard errors with generalised
  linear models (thanks to Thierry Onkelinx)

* geom_vline and geom_hline now correctly transform their intercepts if the
  scale is transformed

* geom_vline and geom_hline: now use xintercept and yintercept instead of intercept

* legend.position and legend.justification work again

* position_dodge now works for any number of elements with smaller widths, not just 2!

* scale_discrete_position: does a better job of calculating axis limits when
  plotting a mixture of continuous and discrete values (e.g. with geom_jitter)

* summary: tweaks to improve output


ggplot2 0.8  (2008-11-18)
----------------------------------------

* The two biggest new features in this release are the (long awaited) ability
  to have scales that vary between facets, and a faceting system that works
  like lattice (facet_wrap). From qplot, you can use facet_wrap by specifying
  one sided formula (~ colour, as opposed to . ~ color). To see some potential
  uses for these new features, see the "Positioning" chapter of the book.
  Implementing these changes has required a rewrite of large parts of the
  coordinate systems code, so if anything seems strange with non-Cartesian
  coordinate systems, please get in touch.

* I've also made another round of tweaks to make the plots more aesthetically
  pleasing.This includes using a bright blue colour for geoms used to add
  statistical summaries to plots (contour, smooth, and quantiles), and
  tweaking the default colour scheme for the continuous colour scale.Please
  let me know what you think.Remember that most of these options are
  controllable with the theming system - see the book chapter "Polishing your
  plots for publication".

* Accompanying this new release of the package is an updated and expanded
  version of the book. The content of the book is now largely complete (~170
  pages), and over the coming months I will be working on make it polished and
  easy to understand.See http://had.co.nz/ggplot2/book.I love to hear your
  feedback about the book, but at this point please don't bother reporting
  minor typos, I would much rather hear about what you want to do, but can't
  figure out from the book.

Other new features:

* geom_bin2d/stat_bin2d & geom_hex/stat_binhex: for 2d square and hexagon binning, particularly useful for alleviating overplotting in scatterplots

* geom_freqpoly: draws frequency polygons (= stat_bin + geom_line)

* scale_position: both discrete and continuous gain a new formatter argument
  to control the default formatting of the axis labels.  See also the handy
  numeric formatters: dollar, comma and percent

* the xlim and ylim functions now produce discrete scales when appropriate,
  and generate a reverse scale if the minimum is greater than the maximum

Improvements

* coord_map gains experimental axis labels

* facet_grid: new support for varying scales in rows and columns

* facet_wrap: new faceter which wraps a 1d ribbon of panels into 2d, in a
  similar way to lattice

* geom_bin: gains a drop argument to control whether or not 0 count bins
  should be removed

* geom_path and geom_line gain arrows argument to match geom_segment

* ggsave now checks that you are using it with a ggplot plot

* ggsave now produces postscript files that are suitable for embedding in
  another document

* ggsave now recognises the .svg extension and will produce svg files, if
  possible

* ggsave: default dpi changed to 300, on the assumption that you are saving
  the plot for printing

* qplot: uses facet_wrap if formula looks like ~ a + b (as opposed to a ~ b)

Aesthetic tweaks

* geom_bar, geom_polygon, geom_rect, ...: default fill colour is now much
  closer to black to match the defaults in other geoms (point, line, etc)

* geom_line, geom_path, geom_segment: lines have squared ends

* geom_point, geom_pointrange and geom_boxplot: now use shape = 16 instead of
  19.  This shape does not have a border from R 2.8 on, and so will look
  better when displayed transparently.

* geom_contour, geom_density2d, geom_quantile and geom_smooth use a bright
  blue colour for lines, to make them stand out when used with black points

* scale_gradient: tweaked default colours to make more aesthetically pleasing

* theme: new theme setting panel.margin (a unit) controls gap between panels
  in facetted plots (for both grid and wrap)

* theme_gray: removed black border around strips

* theme_bw: tweaks to make black and white theme look a little nicer

Bug fixes

* coord_cartesian now correctly clips instead of dropping points outside of its limits

* facet_grid: margins now grouped correctly in default case (non-aesthetic
  variables ignored when generating default group value)

* facet_grid: fix long standing bug when combining datasets with different
  levels of facetting variable

* geom_smooth calls stat::predict explicitly to avoid conflicts with packages
  that override predict for S4 model classes

* grid: correctly expose subcomponents of strips and axes

* mapping aesthetics to functions of stat output now works in a much wider
  variety of cases

* order aesthetic should now work with bars (and in general more geoms)

* position_dodge now works with points and other geoms that lack xmin and xmax

* scale_area works once more

* scale_discrete_position: empty levels are no longer displayed by default, if
  you want them, use breaks = levels(myfactor)

* scale_discrete_position: fixed bug when limits were set

* scale_discrete_position: more aesthetically pleasing expansion for a wider
  ranges of plots (picks expansion based on whether or not geom with width
  used, e.g. bars)

* scale_gradient*: axes are correctly labelled when a transformation is used

* scale_x_log10, scale_y_sqrt etc now correctly transform output from
  statistics as well as raw data

* scale_z_* now removed because no longer used by anything

* stat_bin: correctly returns 0 when no observations in a bin (was previously
  returning NA)

* stat_quantreg: deal with yet another new output format from quantreg

* stat_contour now has arguments to control the position of the contours,
  rather than relying on the z scale

* theme: panel.empty setting removed as it is no longer used

* theme_grey now aliased to theme_gray

* theme_line: setting size works correctly

* theme_rect, theme_segment: size now measured in mm, to be consistent with
  the rest of ggplot

ggplot2 0.7
----------------------------------------------------------------

* ggplot2 0.7 introduces a new theming system which allows you to control
  (almost) every aspect of the appearance of the plot.  This system is
  documented in the book chapter "Polishing your plots for publication",
  available from http://had.co.nz/ggplot2/book/polishing.pdf.

Bugs fixed

* geom_boxplot: now displays outliers even if only one present

* geom_jitter: setting one jitter direction to 0 now works

* geom_segment: should now work correctly in all coordinate systems (note that
  arrows only work in Cartesian coordinates)

* ggsave: correctly uses dpi for raster devices and default dpi changed to 72
  (thanks to Brian Ripley for pointing this out)

* ggsave: current device no longer closes if error occurs

* position_jitter: now works correctly with 0 jitter

* remove_missing: some statistics were calculated incorrectly when missing
  values were present

* scales: extra scales ignored (again)

* scales: legends respect fixed parameters of the layer

* scales: legends won't appear when aesthetics are mapped to NULL, or set to fixed value

* scales: xend and yend now transformed correctly

* scale_date: breaks are now rounded to correct position

New functionality

* geom_point: can now control colour and fill separately for point glyphs with
  borders

* geom_step: now has parameter direction which can take values vh (vertical
then horizontal)  or hv (horizontal then vertical) describing the shape of the
stairs

* qplot: new asp argument to set aspect ratio

* qplot: now captures the environment in which it was run, which should make
  it much more robust at finding the variables you expect it to find

* qplot: now treats any arguments wrapped in I() as parameters, not
  aesthetics, e.g. qplot(mpg, wt, data=mtcars, colour = I("red")) or
  qplot(mpg, wt, data=mtcars, size = I(5))

* scale_continuous: new minor_breaks argument to controls position of minor
  breaks

* scale_discrete: new discrete position scales which make it possible to
  manually position elements

* scale_gradientn: new colour scale which creates gradient between any list of
  colours

More consistent interfaces

* can use color instead of colour, and old R names throughout ggplot2

* geom_jitter: Arguments changed to height and width to match other position
  adjustments

* scales: any point outside of limits is dropped (this was previously the
  behaviour for discrete scales, but not continuous scales)

* scales: limits are consistent across discrete and continuous scales (limits
  c(1, NA) form no longer works for continuous scales)

* scales: order of legends reversed to match order of x axis (and to be
  consistent with previous versions)

* scale_date: new limits argument to set axis limits

* scale_discrete: all discrete scales accept breaks argument

* scale_discrete: all discrete scales have limits and labels argument to
  better control legends

* scale_discrete: character and logical vectors now reliably treated as
  discrete scales

* stat_density2d, geom_density2d: density2d used consistently (instead of
  density_2d in some places)

Improved aesthetics

* coord_polar: more tweaks to grid lines to enhance appearance

* coord_polar: new expand argument to control whether axes should be expanded
  outside the range of the data

* geom_contour, geom_smooth, geom_quantile: now use blue lines

* position_stack, position_dodge: should be more informative if conditions for
  stacking/dodging not met

* position_jitter: default amount of jittering tweaked to align with boxplots
  etc.

* scales: background colour of legends key matches plot

* themes: Complete rewrite of theming system, see new book chapter for details

* themes: direct access to plot options via $ is now disabled

Improved documentation and error messages

* facet_grid: documentation improved

* qplot: Better error messages when needed variables are missing

* scale_discrete: improved error message for too many values in domain

* scale_size: improved documentation for discrete variables

* online documentation generally tweaked and primped to work a little better
 and look a little nicer

* website now includes a search box

* links from rdoc now point to correct pages


ggplot2 0.6
----------------------------------------------------------------

The two big changes in this release are improved documentation and legends.

* all major ggplot2 components now have their own built in documentation, so
  that (e.g.) ?stat_smooth or ?geom_point now give you useful information

* the legend code is now considerably more sophisticated and will attempt to
  merge together legends for the same variable

* also, legends are drawn based on the geoms used (instead of the scales
  used, as previously) so should match the plot much better (e.g. for
  geom_smooth, geom_boxplot, geom_vline, geom_abline, geom_pointrange).

These features are new, so there are likely to be a few bugs that I haven't discovered.  Please me know if you discover any.

Other additions and corrections

* coord_equal: should now work correctly in all situations

* coord_polar: add start and direction parameters, giving more control over
  the layout of the polar coords

* coord_polar: added my favourite pie chart example

* coord_trans now deals with groups appropriately, at the cost of decreased
  speed

* geom_abline, geom_vline, geom_hline: should now behave better in a wider
  variety of settings

* geom_boxplot: deals with continuous x-axis and grouping much better

* geom_boxplot: now has it's own legend which actually looks like a boxplot

* geom_boxplot: reports if missing values removed

* geom_crossbar: the middle line is now display thicker than the other lines,
  controlled by the parameter fatten (thanks to Heike Hofmann for the
  suggestion)

* geom_density: fix scale adjustment bug in geom_density

* geom_line, geom_text: all size measurements (now lines and text as well) are
  measured in mm, lines/paths default to paths 0.5mm wide

* geom_rug: new to add marginal rug plots

* geom_smooth: added example showing how to use geom_smooth with your own
  models

* geom_smooth: fixed bug where if se=FALSE x axis always includes 0

* geom_vline, geom_hline: yet another rewrite which should make them more
  powerful and less error prone.

* ggsave reports width and height of saved image

* position_stack: fixed bug when data was empty

* qplot: allow qplot to use computed aesthetics too

* scale_continuous: tweaks to minor breaks to make appearance better on wider
  range of coordinate systems

* scale_discrete: all discrete scales now have labels argument which you can
  use to override the factor levels

* scale_discrete: now works correctly with character vectors

* scale_size: changed default range to [0.5, 3] to better reflect new sizing
  decisions

* scale_size: legends resize to avoid overlaps

* scale_x_continuous, scale_y_continuous: new convenience functions xlim and
  ylim (and zlim) that make it even easier to adjust the limits of the x, y,
  and z axes

* stat_bin, geom_area: fixed bug in combination of stat_bin and geom_area that
  made it difficult to draw frequency polygons

* stat_bin: fixed bug which resulted in increased counts when the x axis was a
  categorical variable with a single level (thanks to Bob Muenchen for
  pointing this out!)

* stat_bin: no longer incorrectly warns that binwidth is unspecified when
  breaks are set

* stat_bin: now takes origin argument to manually specify origin of first bin
  (default is round_any(min(range), bin_width, floor))

* stat_boxplot, stat_contour, stat_density_2d, stat_qq, stat_density: na.rm
  parameter added to the following statistics (thanks to Leena Choi for
  suggesting this)

* stat_function: new, makes it easy to superimpose a function on the plot

* stat_qq: axes flipped to agree with base R

* stat_qq: now uses sample aesthetic to select variable for summary

* stat_quantile: updated to work with latest version of quantreg

* stat_spoke: new, to make it possible to use geom_segment parameterised by
  angle and radius (thanks to Jiho for the suggestion)

* stat_summary: better documentation

* stat_summary: convenient auto wrapping of simple summary functions

Miscellaneous changes:

* it's now easy to change the default scales (and their arguments) with the
  set_default_scale function, see ?set_default_scale for more details (thanks
  to Bob Muenchen for the suggestion)

* new order aesthetic which controls the order in which elements are plotted

* min and max are now scaled the same way as y

* functions are silently dropped (e.g. aes(colour=col))

* scales do not try and map variables that don't exist (fixes some rather
  obscure bugs)

* aes(mpg, wt) is now equivalent to aes(x = mpg, y = wt)


ggplot2 0.5.7
----------------------------------------------------------------

New geoms, scales and aesthetics

* stat_step and geom_step to draw staircase plots (like plot(type="s"))

* order aesthetic (currently only for lines/paths) allows you to control the
  drawing order within a group

* scale_manual makes it easier to let ggplot uses the exact
  colours/sizes/linetypes that you want

* scale_reverse allows you to reverse the scale of x and y axes

* scale_grey is a new black and white scale for categorical data (colour and
  fill)


Improved options handling

* new function opts() to allow modification of plot options by addition

* update(p, theme_bw) and p + theme_bw now work

These changes mean that you can modify plot options in the same way that you modify all other aspects of the plot, e.g.  qplot(mpg, wt, data=mptcars) + opts(title = "Fuel economy vs weight")

Improved documentation

* many tweaks to the online documentation, particular including the actual
  code you need to run for each object!

* every page now has a link to a form where you can submit feedback on exactly
  you do or don't like about a page

* required aesthetics now listed in documentation

* geom_polygon now has a decent example

* numerous minor corrections suggested by Jörg Beyer

* separated plotting advice from details of plot construction (what vs how),
  thanks to Bert Gunter for this suggestion


Improved map projections (with coord_map)

* coord_map defaults to orientation = c(90, 0, mean(range(y))) - this ensures
  that multiple layers line up correctly, but means you will have to specify
  the orientation yourself for many projections

* coord_map now respects limits set by scales

* removed useless ticks from coord_map

If you're using ggplot to draw maps and have thought of other features that would make your life easier, please let me know.


Bug fixes

* adding data and aesthetics in separate steps should now work

* layers with set parameters will not use mapped aesthetics

* use LazyLoad: false instead of SaveData: true for better future
  compatability

* coord_cartesian: fixed bug that prevented you from overriding the default
  axis expansion

* coord_equal: now scales correctly if ratio < 1

* geom_abline: fix bug where slope was ignored

* geom_jitter now works correctly with groups and categorical values (was
  actually a bug in how scale_discrete deals with continuous values)

* geom_path: automatically switch between polylineGrob and segmentsGrob when
  drawing paths so that setting line type now works properly

* geom_segment now uses both ends of segments to calculate axis limits

* plotmatrix: fix bug in scatterplot matrix where all scatterplots were
  transposed!

* qplot: should now work better within functions

* quickplot added as an alias of qplot, to avoid confusion with qunif, etc

* scale_*: better error message if you add a scale without a matching
  aesthetic mapping in the plot

* scale_identity no longer converts everything to character

* scale_identity: grob argument renamed to guide

* stat_*: made all statistics more robust to errors

* stat_quantile: fixed bug when only drawing a single quantile

* stat_smooth: returns silently if <2 non-missing data points


Minor aesthetic improvements

* coord_polar now specifies aspect.ratio by default, and I've made a few other
  tweaks to make polar coordinates plot look nicer

* geom_bar no longer draws gray borders by default, but instead uses the same
  colour as fill (this eliminates a tiny gap between neighbouring bars)

* plotmatrix: tweaks to improve display of scatterplot matrix

* scale_brewer: added option to reverse palette

* scale_colour: colour and fill legends now look exactly the same (previously
  colour was missing a grey border)

* scale_discrete has slightly larger expansion (0.75 vs 0.5)

* stat_bar: only output bars with > 0 count


ggplot2 0.5.6
----------------------------------------------------------------

Improved error messages and other notifications:

* all geoms and position adjustments should now give an informative error
  message when required aesthetics are missing

* better error messages if data not a data frame, or mapping not created by
  aes or aes_string

* better errors for qplot when variables missing or data invalid

* better error if somehow you are missing necessary scales

* stat_bin informs you of the default choice of binwidth

* stat_smooth gives helpful error messages for common problems

* printing a geom now displays the data set that it uses (if not the default)

Other improvements:

* colour and fill legends now surround by background plot colour

* can now draw arrow heads with geom_segment, and have added an example
  demonstrating drawing a vector field

* density plots should always include 0 on y axis

* default boxplot outlier changed colour to black

* stat_smooth supports categorical variables a little better

* implemented hash methods for all ggplot objects.  This is the first step in
  making it easier for me to compare all examples between versions for quality
  control purposes

New data:

* seals, contributed by David Brillinger and Charlotte Wickham, used for
  vector field example

Bug fixes:

* geoms hline, vline and abline now all work correctly when a grouping variable is used

* block histograms (where individuals are identifiable) now work correctly

* all ggplot objects should now print properly from the command line

* fixed bug in geom_path when only 1 point

* segments geom now works correctly for more coordinate systems

* order variables in scatterplot matrix by order of variables in data.frame

* geom_density deals with missing values correctly when displaying scaled densities

* fixed bug in calculating categorical ranges

* fixed bug in drawing error bars

Subtractions

* now relies on R 2.6

* removed grid.gedit and grid.gremove, and code replaced by grid.ls

ggplot2 0.5.5
----------------------------------------------------------------

Improvements:

* ggplot now gives rather more helpful errors if you have misspecified a
  variable name in the aesthetic mapping

* changed default hline and vline intercepts to 0

* added "count" output variable from stat_density for creating
  stacked/conditional density plots

* added parameters to geom_boxplot to control appearance of outlying points

* overriding aesthetics with fixed values that have already been set with
  aesthetics now actually works

* slightly better names for xaxis and yaxis grobs

* added aes_string function to make it easier to construction aesthetic
  mapping specifications in functions

* continuous scales now have labels argument so that you can manually specify
  labels if desired

* stat_density now calculates densities on a common grid across groups.  This
  means that position_fill and position_stack now work properly

* if numeric, legend labels right aligned

* polar coordinates much improved, and with better examples

Documentation:

* fixed argument documentation for qplot

* added (very) rudimentary documentation about what functions return

* documentation now lists extra variables created by statistics

Bug fixes:

* coord_flip now works with segment and all interval geoms

* geom_errorbar now works in all coordinate systems

* derived y axes (eg. on histogram) are now labelled correctly

* fixed bug in stat_quantile caused by new output format from predict.rq

* fixed bug if x or y are constant

* fixed bug in histogram where sometimes lowest bar was omitted

* fixed bug in stat_qq which prevent setting aesthetics

* fixed bug in qplot(..., geom="density", position="identity")

* fixed stat_qq so that unnecessary arguments are no longer passed to the
  distribution function

Subtractions:

* removed grid argument from ggsave, replaced by ggtheme(theme_bw)

* removed add argument from qplot


ggplot2 0.5.4
----------------------------------------------------------------

* border now drawn on top of geoms, instead of below - this results in better
  appearance when adjusting scale limits

* ggplot() + aes() now modifies existing default aesthetic mapping, rather
  than overwriting

* polish examples in facet_grid

ggplot2 0.5.3
----------------------------------------------------------------

* added experimental scatterplot matrix, see ?plotmatrix

* added new border.colour and grid.minor.colour options for better control
  over plot apperance

* updated theme_bw to do better when drawing a plot with white background

* better default colour choices for gradients (and more discussion in examples)

* fixed bug in ScaleGradient2 where scales with different positive and
  negative ranges were not scaled correctly

* allow expressions as result from strip.text

* fixed rare bug in geom_vline and geom_hline

* fixed example in geom_abline

* tweaked display of multiline axis labels

ggplot2 0.5.2
----------------------------------------------------------------

* add argument to position dodge so it's now possible to accurately dodge things with different widths to their physical widths

* added median summary

New examples:

* logistic regression example in stat_smooth

Bugs fixed:

* evaluation of arguments to layer is no longer delayed

* can use categorical xseq with stat_smooth

* x and y axes named incorrectly (thanks to Dieter Menne for spotting this)

* can now pass position objects to qplot

* y jitter calculated correctly, and jittered data rescales axis now

* removed silly legend from quantile plot

* extra arguments not being passed on to geoms/stats

* fixed bug in stat_summary when summarising a factor

* fixed bugs in stat_summary, geom_ribbon, and coord_trans examples

ggplot2 0.5.1
----------------------------------------------------------------

* renamed scale_manual to scale_identity to map position_identity and
  stat_identity

* ensured all grob consistently named

* renamed aesthetics argument to mapping to be consistent with description in
  book

* added useful utilities for modifying grobs

* bug fixes to x axis range with interval geoms

* added ability to turn legend off for single scale (currently undocumented)

* added economics data set and matching examples

ggplot2 0.5
----------------------------------------------------------------

* complete rewrite of ggplot code base

* id/grouping completely rewritten so that automatically grouped when any of
  the aesthetics is a categorical variable.This behaviour is defined in the
  Grammar of Graphics, and makes things like qplot(wt, data=mtcars,
  geom="density", colour=factor(cyl)) work nicely