[Rd] axis, title & padj
plfjohnson at emory.edu
Wed Mar 2 23:38:02 CET 2011
I often use par(mex = 0.5) as an easy way to shrink space used for
margins. However, I recently noticed that this leads to an asymmetry in
the positioning of the x vs. y axis labels and xlab / ylab -- the x-axis
labels are pushed into the tic-marks, while the y-axis labels look fine.
A more extreme example:
Tracking this down in the code, this effect appears to be arising from:
1) GMtext in graphics.c adjusts the margin line coordinate using
dev->yLineBias. After commenting out these adjustments, the x-axis text
is clearly shifted up (i.e. the bottom of the text is aligned at the
specified margin line) while the y-axis text is shifted left (i.e. the
bottom of the text is still aligned with the specified margin line).
2) This observation lead me to realize that do_axis and do_title in
plot.c assume padj=0 most of the time (there are exceptions depending on
I'm no expert in the R code base, but the yLineBias adjustments appears
like they might have been intended to restore symmetry -- but it only
works for mex=1.
Is there a reason why, instead of yLineBias, we can't either:
1) center axis and title text by default (i.e. padj=0.5)
2) align side=1,3 with padj=1; side=2,4 with padj=0
Solution 1 is trivial to implement, but this would shift positioning
slightly relative to the current code (even for mex=1).
Solution 2 is slightly trickier because we have to pay attention to side
and las values, but would not change the output for mex=1.
I implemented drafts of both solutions, which work at least
superficially. Two questions:
-Am I missing a larger purpose to yLineBias?
-Thoughts about which solution is better / can I contribute a patch
to fix this?
More information about the R-devel