[R] Plotmath with values?

[Charles C. Berry]

On Wed, 31 Dec 2008, Mike Prager wrote:

> I hope to use the plotmath facility to print titles that mix
> math and values of R variables.
>
> The help for "plotmath" has an example, which after repeated
> reading, I find baffling. Likewise, I have read the help file
> for "substitute" (wqhich seems to be needed) without ever
> understanding what it does, other than being used in some magic
> incantations.
>
> I would like to do something like this:
>
>     dev.new()
>     aa <- round(pi,2)
>     plot(1:3, 1:3, main = ~ a == aa)


It has another example, too, along these lines:

 	 plot(1:3, 1:3, main = bquote(a == .(aa)))


You have to follow a couple of 'See Also' links from the plothmath page to 
get to

 	?bquote

HTH,

Chuck


>
> and have the main title read "a = 3.14"
>
> but of course it reads "a = aa".
>
>> From a user's point of view -- one who has never written a
> parser nor taken a course in compilers -- what is needed is the
> nonexistent function "value" usable in plotmath expressions to
> produce the value of its argument, as
>
>     plot(1:3, 1:3, main = ~ a == value(aa))
>
> How can this be done?
>
> THANKS!
>
> -- 
> Mike Prager, NOAA, Beaufort, NC
> * Opinions expressed are personal and not represented otherwise.
> * Any use of tradenames does not constitute a NOAA endorsement.
>
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>

Charles C. Berry                            (858) 534-2098
                                             Dept of Family/Preventive Medicine
E mailto:cberry at tajo.ucsd.edu	            UC San Diego
http://famprevmed.ucsd.edu/faculty/cberry/  La Jolla, San Diego 92093-0901