Greek characters in plots

OK, I am definitely struggling here.

The text I am trying to plot isn't a mathematical expression, it's:

A) ?stbA::cat 

This is biological notation for a particular mutation.  The "A)" part is a tag identifying the graph, and the "stbA::cat" bit is the gene that is mutated.  Both the tag and gene are set as variables in a loop, and only the delta remains the same.

As the text I am trying to plot isn't a mathematical expression, I seem to be having trouble getting substitute() and expression() to do what I want.  As plotmath states "A mathematical expression must obey the normal rules of syntax for any R expression", I fear I may be barking up the wrong tree!

Thank you all for your help so far, but can someone please help me once more and tell me how I can get the capital Delta symbol so I can use it in non-mathematical text and strings for plotting?

Thanks once again

Mick  

-----Original Message-----
From: Prof Brian Ripley [mailto:ripley at stats.ox.ac.uk] 
Sent: 05 August 2008 12:40
To: michael watson (IAH-C)
Cc: Henrique Dallazuanna; r-help at r-project.org
Subject: Re: [R] Greek characters in plots

Excellent!  I even tried DELTA but not Delta....

?plotmath says

       'Alpha' - 'Omega'               uppercase Greek symbols

How could that be made clearer?

(Note it carefully says Greek *symbols* not *character*: they are not the
same thing.)

Now, how do I go about pasting that with some text that I have in various other variables?

Use substitute?  E.g.

substitute(expression(foo*Delta), list(foo=3))

(Some people prefer bquote, but that is just a wrapper for substitute in 
R.)

-----Original Message-----
From: Henrique Dallazuanna [mailto:wwwhsd at gmail.com]
Sent: 05 August 2008 12:17
To: michael watson (IAH-C)
Cc: r-help at r-project.org
Subject: Re: [R] Greek characters in plots

Try,

expression(Delta)

On Tue, Aug 5, 2008 at 8:14 AM, michael watson (IAH-C)
<michael.watson at bbsrc.ac.uk> wrote:

Hi

I am running an R script that creates 100s of graphs, and I need to use
the greek CAPITAL letter delta in the mtext() function.

I got as far as expression(delta) but this gives me the lowercase
version.

Can anyone help?  I'm using R 2.7 on Windows XP

Mick

Head of Informatics
Institute for Animal Health
Compton
Berks
RG20 7NN
01635 578411

http://www.iah.ac.uk/research/bioinformatics/bioinf.shtml

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-- 
Henrique Dallazuanna
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25? 25' 40" S 49? 16' 22" O

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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.

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)
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