geom_path.Rd

% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/geom-path.r
\name{geom_path}
\alias{geom_path}
\alias{geom_line}
\alias{geom_step}
\title{Connect observations}
\usage{
geom_path(mapping = NULL, data = NULL, stat = "identity",
  position = "identity", ..., lineend = "butt", linejoin = "round",
  linemitre = 1, arrow = NULL, na.rm = FALSE, show.legend = NA,
  inherit.aes = TRUE)

geom_line(mapping = NULL, data = NULL, stat = "identity",
  position = "identity", na.rm = FALSE, show.legend = NA,
  inherit.aes = TRUE, ...)

geom_step(mapping = NULL, data = NULL, stat = "identity",
  position = "identity", direction = "hv", na.rm = FALSE,
  show.legend = NA, inherit.aes = TRUE, ...)
}
\arguments{
\item{mapping}{Set of aesthetic mappings created by \code{\link[=aes]{aes()}} or
\code{\link[=aes_]{aes_()}}. If specified and \code{inherit.aes = TRUE} (the
default), it is combined with the default mapping at the top level of the
plot. You must supply \code{mapping} if there is no plot mapping.}

\item{data}{The data to be displayed in this layer. There are three
options:

If \code{NULL}, the default, the data is inherited from the plot
data as specified in the call to \code{\link[=ggplot]{ggplot()}}.

A \code{data.frame}, or other object, will override the plot
data. All objects will be fortified to produce a data frame. See
\code{\link[=fortify]{fortify()}} for which variables will be created.

A \code{function} will be called with a single argument,
the plot data. The return value must be a \code{data.frame.}, and
will be used as the layer data.}

\item{stat}{The statistical transformation to use on the data for this
layer, as a string.}

\item{position}{Position adjustment, either as a string, or the result of
a call to a position adjustment function.}

\item{...}{other arguments passed on to \code{\link[=layer]{layer()}}. These are
often aesthetics, used to set an aesthetic to a fixed value, like
\code{color = "red"} or \code{size = 3}. They may also be parameters
to the paired geom/stat.}

\item{lineend}{Line end style (round, butt, square)}

\item{linejoin}{Line join style (round, mitre, bevel)}

\item{linemitre}{Line mitre limit (number greater than 1)}

\item{arrow}{Arrow specification, as created by \code{\link[grid:arrow]{grid::arrow()}}}

\item{na.rm}{If \code{FALSE}, the default, missing values are removed with
a warning. If \code{TRUE}, missing values are silently removed.}

\item{show.legend}{logical. Should this layer be included in the legends?
\code{NA}, the default, includes if any aesthetics are mapped.
\code{FALSE} never includes, and \code{TRUE} always includes.}

\item{inherit.aes}{If \code{FALSE}, overrides the default aesthetics,
rather than combining with them. This is most useful for helper functions
that define both data and aesthetics and shouldn't inherit behaviour from
the default plot specification, e.g. \code{\link[=borders]{borders()}}.}

\item{direction}{direction of stairs: 'vh' for vertical then horizontal, or
'hv' for horizontal then vertical}
}
\description{
\code{geom_path()} connects the observations in the order in which they appear
in the data. \code{geom_line()} connects them in order of the variable on the
x axis. \code{geom_step()} creates a stairstep plot, highlighting exactly
when changes occur. The \code{group} aesthetic determines which cases are
connected together.
}
\details{
An alternative parameterisation is \code{\link[=geom_segment]{geom_segment()}}: each line
corresponds to a single case which provides the start and end coordinates.
}
\section{Aesthetics}{

\aesthetics{geom}{path}
}

\examples{
# geom_line() is suitable for time series
ggplot(economics, aes(date, unemploy)) + geom_line()
ggplot(economics_long, aes(date, value01, colour = variable)) +
  geom_line()

# geom_step() is useful when you want to highlight exactly when
# the y value chanes
recent <- economics[economics$date > as.Date("2013-01-01"), ]
ggplot(recent, aes(date, unemploy)) + geom_line()
ggplot(recent, aes(date, unemploy)) + geom_step()

# geom_path lets you explore how two variables are related over time,
# e.g. unemployment and personal savings rate
m <- ggplot(economics, aes(unemploy/pop, psavert))
m + geom_path()
m + geom_path(aes(colour = as.numeric(date)))

# Changing parameters ----------------------------------------------
ggplot(economics, aes(date, unemploy)) +
  geom_line(colour = "red")

# Use the arrow parameter to add an arrow to the line
# See ?arrow for more details
c <- ggplot(economics, aes(x = date, y = pop))
c + geom_line(arrow = arrow())
c + geom_line(
  arrow = arrow(angle = 15, ends = "both", type = "closed")
)

# Control line join parameters
df <- data.frame(x = 1:3, y = c(4, 1, 9))
base <- ggplot(df, aes(x, y))
base + geom_path(size = 10)
base + geom_path(size = 10, lineend = "round")
base + geom_path(size = 10, linejoin = "mitre", lineend = "butt")

# NAs break the line. Use na.rm = T to suppress the warning message
df <- data.frame(
  x = 1:5,
  y1 = c(1, 2, 3, 4, NA),
  y2 = c(NA, 2, 3, 4, 5),
  y3 = c(1, 2, NA, 4, 5)
)
ggplot(df, aes(x, y1)) + geom_point() + geom_line()
ggplot(df, aes(x, y2)) + geom_point() + geom_line()
ggplot(df, aes(x, y3)) + geom_point() + geom_line()

\donttest{
# Setting line type vs colour/size
# Line type needs to be applied to a line as a whole, so it can
# not be used with colour or size that vary across a line
x <- seq(0.01, .99, length.out = 100)
df <- data.frame(
  x = rep(x, 2),
  y = c(qlogis(x), 2 * qlogis(x)),
  group = rep(c("a","b"),
  each = 100)
)
p <- ggplot(df, aes(x=x, y=y, group=group))
# These work
p + geom_line(linetype = 2)
p + geom_line(aes(colour = group), linetype = 2)
p + geom_line(aes(colour = x))
# But this doesn't
should_stop(p + geom_line(aes(colour = x), linetype=2))
}
}
\seealso{
\code{\link[=geom_polygon]{geom_polygon()}}: Filled paths (polygons);
\code{\link[=geom_segment]{geom_segment()}}: Line segments
}