[Rd] Re: argument srt for mtext(); was: [R] using text on the x axis ticks rather than numbers

Prof Brian Ripley ripley at stats.ox.ac.uk
Wed Sep 8 08:57:46 CEST 2004

On Wed, 8 Sep 2004, Uwe Ligges wrote:

> Prof Brian Ripley wrote:
> > On Tue, 7 Sep 2004, Adaikalavan Ramasamy wrote:
> > 
> > 
> >>Out of curiosity, why is srt not respected in mtext ? See examples below
> > 
> > 
> > It doesn't make a lot of sense.  mtext is about putting text on >m<argin
> > lines, and even the ability to have text perpendicular to the axis (via
> > las) is rather awkward to interpret (and the interpretation will be
> > changed in 2.0.0).  If you are going to rotate text you need to able to
> > specify a point of rotation and that's much easier via text.
> > 
> > 
> >>It would be nice to have 'srt' as an argument in mtext in future.
> > 
> > 
> > You haven't been listening to the discussions pre-2.0.0 on the semantics
> > of `adj' (and now padj as well) in mtext.  Experts seem to find it hard to
> > keep even the two current cases (parallel and perpendicular) clear in
> > their minds.
> [moved to R-devel]
> The discussions took place on R-devel, hence some people might not have 
> noticed them.

Yes, and that's why they `haven't been listening to' them.

> Indeed, I think it is possible to provide an srt command (e.g. in half a 
> year for something like R-2.1.0). What is expected for "srt = 0"?
> a) the current behaviour, i.e. srt=0 in respect to the las setting *and* 
> the margin side to plot the text in, or
> b) always horizontally drawn text?
> I'd vote for b).

That's easy, see the precedent in

> > BTW, if you want to use srt with mtext(at=) you can always use S ....

S ignores las if at= is set, so srt=0 is the current default behaviour.

Where exactly do you rotate about?  I suspect people want the corner 
nearest the axis for near-perpendicular text.  Corner of what?  Probably 
not the actual bounding box but some nomimal bounding box for the font.

Remember the default centring is different for parallel and perpendicular 
text, so what should it be for 45^o text?

I have quite a bit of experience with using S's mtext with srt, and it is 
hard to use well (and very hard to document).


Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
Oxford OX1 3TG, UK                Fax:  +44 1865 272595

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