[Rd] Is text(..., adj) upside down? (Or am I?)

[Prof Brian Ripley]

On Tue, 22 Jul 2008, Patrick Burns wrote:

> Basically the only thing in the thread that was clear
> to me was Brian's phrasing.  So I'd suggest basing
> any changes on that.

I'll add some words.  There is one other thing which needs explaining, 
what 'bottom' means.  For a character string it means the baseline of the 
text, for an expression the bottom of the text box (plotmath) does not 
attempt to compute baselines.  This also affects the computation of 
vertical centering:

plot(1:5, type="n")
abline(v=2); abline(v=4)
abline(h=1)
text(2,1, "fgh", adj=c(0,0), cex=2)
text(4,1, expression(fgh), adj=c(0,0), cex=2)
abline(h=3)
text(2,3, "fgh", adj=c(0,0.5), cex=2)
text(4,3, expression(fgh), adj=c(0,0.5), cex=2)
abline(h=5)
text(4,5, expression(fgh), adj=c(0,1), cex=2)
text(2,5, "fgh", adj=c(0,1), cex=2)

>
>
> Patrick Burns
> patrick at burns-stat.com
> +44 (0)20 8525 0696
> http://www.burns-stat.com
> (home of S Poetry and "A Guide for the Unwilling S User")
>
> S Ellison wrote:
>> Yup; you're all right - it IS consistent (and I'd even checked the x-adj
>> and it did what I expected!!). It's just that ?text is talking about the
>> position of the 'anchor' point in the text region rather than the
>> subsequent location of the centre of the text.
>> 
>> Anyway; if anyone is considering a minor tweak to ?text, would it be
>> clearer if it said "Values of 0, 0.5, and 1 specify text towards right/top, 
>> middle and
>> left/bottom of x,y,      respectively." ?
>> 
>> (or, of course, "Values of 0, 0.5, and 1 specify x,y at left/bottom,
>> middle and right/top of text, respectively.")
>> 
>> Steve Ellison
>> Lab of the Government Chemist
>> UK
>> 
>> 
>> 
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-- 
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