Tuesday, August 5, 2014

Rotated axis labels in R plots

It's somehow amazing to me that the option for slanted or rotated axes labels is not an option within the basic plot() or axis() functions in R.  The advantage is mainly in saving plot area space when long labels are needed (rather than as a means of preventing excessive head tilting). The topic is briefly covered in this FAQ, and the solution is a bit tricky, especially for a new R user. Below is an example of this procedure.

To reproduce example:

# Example data
tmin <- as.Date("2000-01-01")
tmax <- as.Date("2001-01-01")
tlab <- seq(tmin, tmax, by="month")
lab <- format(tlab,format="%Y-%b")
x <- seq(tmin, tmax, , 100)
y <- cumsum(rnorm(100))
# Plot
png("plot_w_rotated_axis_labels.png", height=3, width=6, units="in", res=400)
op <- par(mar=c(6,4,1,1))
plot(x, y, t="l", xaxt="n", xlab="")
axis(1, at=tlab, labels=FALSE)
text(x=tlab, y=par()$usr[3]-0.1*(par()$usr[4]-par()$usr[3]),
labels=lab, srt=45, adj=1, xpd=TRUE)
Created by Pretty R at inside-R.org

1 comment:

  1. agreed...
    It drives me crazy each time I have to do this trick...
    And when saving as an image, if the labels are really long, it won't fit into it... so I have to reduce the label's size or increase the rotation :(