geom_raster.Rd

% Generated by roxygen2 (4.1.0): do not edit by hand
% Please edit documentation in R/geom-raster.r
\name{geom_raster}
\alias{geom_raster}
\title{High-performance rectangular tiling.}
\usage{
geom_raster(mapping = NULL, data = NULL, stat = "identity",
  position = "identity", hjust = 0.5, vjust = 0.5, interpolate = FALSE,
  ...)
}
\arguments{
\item{mapping}{The aesthetic mapping, usually constructed with
\code{\link{aes}} or \code{\link{aes_string}}. Only needs to be set
at the layer level if you are overriding the plot defaults.}

\item{data}{A layer specific dataset - only needed if you want to override
the plot defaults.}

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

\item{position}{The position adjustment to use for overlapping points
on this layer}

\item{hjust,vjust}{horizontal and vertical justification of the grob.  Each
justification value should be a number between 0 and 1.  Defaults to 0.5
for both, centering each pixel over its data location.}

\item{interpolate}{If \code{TRUE} interpolate linearly, if \code{FALSE}
(the default) don't interpolate.}

\item{...}{other arguments passed on to \code{\link{layer}}. This can
include aesthetics whose values you want to set, not map. See
\code{\link{layer}} for more details.}
}
\description{
This is a special case of \code{\link{geom_tile}} where all tiles are
the same size.  It is implemented highly efficiently using the internal
\code{rasterGrob} function.
}
\details{
By default, \code{geom_raster} add a vertical and horizontal padding.
The size of padding depends on the resolution of data.
If you want to manually set the padding (e.g. want zero-padding),
you can change the behavior by setting \code{hpad} and \code{vpad}.
}
\section{Aesthetics}{

\Sexpr[results=rd,stage=build]{ggplot2:::rd_aesthetics("geom", "raster")}
}
\examples{
\donttest{
# Generate data
pp <- function (n,r=4) {
 x <- seq(-r*pi, r*pi, len=n)
 df <- expand.grid(x=x, y=x)
 df$r <- sqrt(df$x^2 + df$y^2)
 df$z <- cos(df$r^2)*exp(-df$r/6)
 df
}
qplot(x, y, data = pp(20), fill = z, geom = "raster")
# Interpolation worsens the apperance of this plot, but can help when
# rendering images.
qplot(x, y, data = pp(20), fill = z, geom = "raster", interpolate = TRUE)

# For the special cases where it is applicable, geom_raster is much
# faster than geom_tile:
pp200 <- pp(200)
base <- ggplot(pp200, aes(x, y, fill = z))
benchplot(base + geom_raster())
benchplot(base + geom_tile())

# justification
df <- expand.grid(x = 0:5, y = 0:5)
df$z <- runif(nrow(df))
# default is compatible with geom_tile()
ggplot(df, aes(x, y, fill = z)) + geom_raster()
# zero padding
ggplot(df, aes(x, y, fill = z)) + geom_raster(hjust = 0, vjust = 0)
}
}