[R] forcing all tick labels to plot
Marc Schwartz
MSchwartz at MedAnalytics.com
Wed Jan 19 22:12:13 CET 2005
On Wed, 2005-01-19 at 15:43 -0500, William Briggs wrote:
> I'm trying to find a way to force all the x-axis tick labels to plot,
> regardless whether or not they overlap or look pretty.
>
> V is a factor with, say, 4 levels. A call to plot(V) gives a
> histogram-like plot, one bar for each level in V. The problem is that
> all the label names may not be plotted because some of the names are
> lengthy and would tend to overlap if plotted.
>
> I don't care if they do, I want to see all the labels, overplotted or not.
>
> I tried:
>
> plot(V,axes=F)
> d<-levels(V)
> axis(1,at=1:4,label=d)
> axis(2)
>
> But this does nothing more than the default, that is, only some of the
> labels print. The other problem is the "at=1:4", which is my guessing
> where the tickmarks go. The function "axTicks(1)" may help, but it
> frequently has more tick marks then levels in "V", so again I have to
> guess which goes where.
>
> I see this:
>
> c<-par()
> c$xaxp = 0.5 3.5 4
>
> or something similar. Is there another par() in which the tick marks
> that are calculated are given explicitly?
>
> I have tried:
>
> par(cex=.7)
>
> and that works for some V, but not for all, and it isn't a very general
> solution.
>
> Is there some flag that I can set to force all the tick labels to plot?
>
> Matt Briggs
plot.factor() is the plot method used in this case. Since it uses
barplot() internally, it will return the bar midpoints invisibly (which
I noted is not defined as a return value in the help for plot.factor)
You can then use mtext() to force the drawing of the labels:
# Draw the plot, but not the x axis
# This example presumes V is a four level factor
mp <- plot(V, xaxt = "n")
# Create some long labels
labels <- c(paste("Very Very Very Long Label Here", 1:4, sep = ""))
# Now plot the labels below the bar midpoint
mtext(side = 1, labels, at= mp, line = 1)
That should do it.
See ?mtext and ?barplot for more information.
HTH,
Marc Schwartz
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