Skip to content


Subversion checkout URL

You can clone with
Download ZIP
Fetching contributors…
Cannot retrieve contributors at this time
74 lines (63 sloc) 2.28 KB
\title{Horizontal line.}
geom_hline(mapping = NULL, data = NULL, stat = "hline",
position = "identity", show_guide = FALSE, ...)
\item{show_guide}{should a legend be drawn? (defaults to
\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
overlappling points on this layer}
\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.}
This geom allows you to annotate the plot with horizontal
lines (see \code{\link{geom_vline}} and
\code{\link{geom_abline}} for other types of lines).
There are two ways to use it. You can either specify the
intercept of the line in the call to the geom, in which
case the line will be in the same position in every
panel. Alternatively, you can supply a different
intercept for each panel using a data.frame. See the
examples for the differences
p <- ggplot(mtcars, aes(x = wt, y=mpg)) + geom_point()
p + geom_hline(aes(yintercept=mpg))
p + geom_hline(yintercept=20)
p + geom_hline(yintercept=seq(10, 30, by=5))
# With coordinate transforms
p + geom_hline(aes(yintercept=mpg)) + coord_equal()
p + geom_hline(aes(yintercept=mpg)) + coord_flip()
p + geom_hline(aes(yintercept=mpg)) + coord_polar()
# To display different lines in different facets, you need to
# create a data frame.
p <- qplot(mpg, wt, data=mtcars, facets = vs ~ am) <- data.frame(z = 1:4, vs = c(0,0,1,1), am = c(0,1,0,1))
p + geom_hline(aes(yintercept = z),
\code{\link{geom_vline}} for vertical lines,
\code{\link{geom_abline}} for lines defined by a slope
and intercept, \code{\link{geom_segment}} for a more
general approach
Jump to Line
Something went wrong with that request. Please try again.