Hi

This is a basic "feature" of both strheight() and stringHeight(). They both ignore any descenders in the text. I cannot remember why it was done this way originally. The future solution is probably to add an argument that allows descenders to be included in text height.

Plotmath works on bounding boxes so its behaviour is different, but of course that has its own problems because there is no sense of "baseline" for expressions.

Paul

On 27/04/2011 11:06 a.m., baptiste auguie wrote:
Dear all,

I'm puzzled by the behavior of stringHeight in the grid package.
Consider the following test,

library(grid)

test<- function(lab="dog", ...){
   g1<- textGrob(lab)
   g2<- rectGrob(height=grobHeight(g1), width=grobWidth(g1))
   gg<- gTree(children=gList(g1,g2), ...)

   print(c("height:", convertUnit(stringHeight(lab), "mm", "y")))
   grid.draw(gg)
}

grid.newpage()
test()
test(expression(dog), vp=viewport(x=0.6))
## notice how the dog's tail is being cut off, where
## expression yields a snug cage

grid.newpage()
test("aoc")
test(expression(aoc), vp=viewport(x=0.6))

It appears that stringHeight correctly calculates the height for an
expression, but not for a basic string. I think it used to produce the
same output for both.

Best regards,

baptiste

sessionInfo()
R version 2.13.0 alpha (2011-03-27 r55076)
Platform: i386-apple-darwin9.8.0 (32-bit)

locale:
[1] C

attached base packages:
[1] stats     graphics  grDevices utils     datasets  grid      methods
[8] base

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Dr Paul Murrell
Department of Statistics
The University of Auckland
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p...@stat.auckland.ac.nz
http://www.stat.auckland.ac.nz/~paul/

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