[R] Combining math and variables in expression

[David Winsemius]

Dear socrates;

It did not take me 2.5 hours but it did take longer than I thought it  
would. I worked off the example given by Henrique Dallazuanna seen at:
http://finzi.psych.upenn.edu/R/Rhelp08/archive/120065.html

  This seems "to work":

mtext(bquote(100~"%" ~ Area == ~ .(text.val)~ Km^2), side=3)

I cannot say the the syntactic rules are entirely clear. The proper  
placement of the tildes is a bit mysterious to me. I am wondering if a  
solution using substitute(expression(.)) might be more clear but my  
efforts in that direction were not successful.

--

David

On Mar 11, 2009, at 10:08 AM, socrates wrote:

>
> I am trying to get the following line in a plot margin using mtext:
>
> 100% Area = 120.000 km^2
>
> Where I intend that "100% Area =" is text, 120.000 is a number that  
> varies
> according to different data, and km^2 should be a neat
> km-with-superscript-2.
> The expression function fails me, since it apparently cannot coerce an
> expression when a variable is involved.
> In the R help file there is an example using either bquote or  
> substitute to
> accomplish like things, but these are sufficiently different from my
> objective and I am becoming more and more confused by every further  
> example
> I stumble on.
> This should be easy. Can anyone help me prevent spending anoter 2.5  
> hours on
> the matter? Thanks.
> -- 
> View this message in context: http://www.nabble.com/Combining-math-and-variables-in-expression-tp22455877p22455877.html
> Sent from the R help mailing list archive at Nabble.com.
>
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David Winsemius, MD
Heritage Laboratories
West Hartford, CT