geom_hline {ggplot2} | R Documentation |
This geom allows you to annotate the plot with horizontal
lines (see geom_vline
and
geom_abline
for other types of lines).
geom_hline(mapping = NULL, data = NULL, stat = "hline", position = "identity", show_guide = FALSE, ...)
show_guide |
should a legend be drawn? (defaults to
|
mapping |
The aesthetic mapping, usually constructed
with |
data |
A layer specific dataset - only needed if you want to override the plot defaults. |
stat |
The statistical transformation to use on the data for this layer. |
position |
The position adjustment to use for overlappling points on this layer |
... |
other arguments passed on to
|
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
geom_hline
understands the following aesthetics (required aesthetics are in bold):
alpha
colour
linetype
size
geom_vline
for vertical lines,
geom_abline
for lines defined by a slope
and intercept, geom_segment
for a more
general approach
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) hline.data <- data.frame(z = 1:4, vs = c(0,0,1,1), am = c(0,1,0,1)) p + geom_hline(aes(yintercept = z), hline.data)