Hi
Uwe Ligges wrote:
[EMAIL PROTECTED] wrote:
[EMAIL PROTECTED] wrote:
Dear all,
Our quite basic function mtext() does wrong adjustments in some parameter
configurations. This gets obvious when using multi line texts: There is no
way to properly adjust text perpendicular to axis 2, for example.
Best
Jens Oehlschlägel
m <- matrix(1:9, 3) colnames(m) <- c("several\nlines", "several\nlines", "several\nlines")
par(mfrow=c(2,2))
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0 adj=0.5 is
fine")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0, adj=0.5)
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0 adj=1 is
different")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0, adj=1)
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=1 adj=0.5 is
NOT fine")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=0.5)
barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="at las=1, adj=1
works the wrong direction", sub="no way to get adj=c(1, 0.5) with las=1 (or
2)")
mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=1)
par(mfrow=c(1,1))
Left / right adjustemnt seems to be perfectly OK.
The thing that matters is centering "several lines" to the specified ("at=") location.
In fact, mtext() is not centering but bottom-aligning by adding a negative distance that looks OK for one line in the default font size, but not in most other cases.
Hence this is the same as Paul Murrell's PR#1659 ("mtext() alignment of perpendicular text"). Fixing this, and/or improving mtext()'s "adj" argument to accept 2 dimensions is desirable, but might be not that easy... I'll take a look during the next days, but nothing promised.
Uwe Ligges
Having looked into the code, there are three possible solution (all with
some drawbacks) I can see. Well, the current argument "adj" becomes
"xadj" in the C sources (graphics.c, GMtext), and "yadj" is set to 0. Hence the ugly hard coded LineBias of 0.3.
Solutions
=========
1: Hardcode "yadj" to 0.5 and remove all those 0.3 biases. Looks good for axes, but it might break some code --> bad.
On the other hand, GMMathText has hardcoded yadj=0.5. Is there a problem with some special devices? Or any other reason not to center stuff using "adj=0.5"?
2: Allow the typical 2-value adj, take the first as xadj, the second one as yadj. This might break some code, because currently adj of arbitrary length (!=0) is allowed and recycled.
3: Invent an argument "padj" for mtext() that represents adjustment *p*erpendicular to the text direction and gets mapped to "yadj" in GMtext. In that case the hardcoded 0.3 bias mentioned above can be removed. The question is whether to set the default to 0.5 (will still break code, but easily to fix by setting padj to 0).
I'd like to propose the third solution and would be happy to provide a
patch of GMText, including corresponding patches to GMMathText, as well as mtext(), title() and axis() (and their inderlying do_* components).
Are there any objections? Any reasons not to do it?
It hurts my head to think about this stuff. There are so many combinations to worry about:
(i) The las setting
(ii) The axis (bottom, left, top, right)
(iii) Whether adj has been specified
(iv) Whether the text is multi-line
I think mtext() does ok as long as adj is not specified and the text is single-line.
I would suggest addressing the multi-line problem for unspecified adj as a first step. And I will definitely not mourn the passing of the 0.3 constant. Setting yadj to 0.5 is not enough though because that doesn't make sense for multi-line text that is parallel to an axis (in that case, yadj should probably be 0 for axis 2 and 3 and 1 for axis 1 and 4; did I mention that there are lots of combinations to worry about?).
For user-specified adj, I agree that a 2-value adj is not a good solution (adj is assumed to be horizontal adjustment) so maybe a padj would be best to allow user control of vertical alignment.
Paul -- Dr Paul Murrell Department of Statistics The University of Auckland Private Bag 92019 Auckland New Zealand 64 9 3737599 x85392 [EMAIL PROTECTED] http://www.stat.auckland.ac.nz/~paul/
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