[Rd] mtext adj= wrong with several las= (PR#7188)
p.murrell at auckland.ac.nz
Tue Aug 24 01:39:42 CEST 2004
Uwe Ligges wrote:
> ligges at statistik.uni-dortmund.de wrote:
>> joehl at gmx.de wrote:
>>> Dear all,
>>> Our quite basic function mtext() does wrong adjustments in some
>>> configurations. This gets obvious when using multi line texts: There
>>> is no
>>> way to properly adjust text perpendicular to axis 2, for example.
>>> Jens Oehlschlägel
>>> m <- matrix(1:9, 3)
>>> colnames(m) <- c("several\nlines", "several\nlines", "several\nlines")
>>> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0
>>> adj=0.5 is
>>> mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=0,
>>> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="las=0 adj=1 is
>>> 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,
>>> barplot(m, horiz=TRUE, axes=FALSE, axisnames=FALSE, main="at las=1,
>>> works the wrong direction", sub="no way to get adj=c(1, 0.5) with
>>> las=1 (or
>>> mtext(colnames(m), 2, at=seq(0.5+0.2, by=1+0.2, length=3), las=1, adj=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.
> 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
> 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
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.
Dr Paul Murrell
Department of Statistics
The University of Auckland
Private Bag 92019
64 9 3737599 x85392
paul at stat.auckland.ac.nz
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