[R] vectorized plotmath expressions via substitute()

[William Dunlap]

I recommend using bquote(), with its .() substitution operator, instead of
substitute any time you use plotmath.    To make a vector of plotmath
expressions use the following sort of as.expression(lapply(... bquote ...)) idiom:

  plot(1:10, axes=FALSE)
  at <- axTicks(1)
  lab <- as.expression(lapply(at, function(a)bquote(10^.(a))))
  axis(1, at=at, lab=lab)

Bill Dunlap
Spotfire, TIBCO Software
wdunlap tibco.com


> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org] On Behalf
> Of Murat Tasan
> Sent: Wednesday, November 14, 2012 9:06 AM
> To: r-help at r-project.org
> Subject: [R] vectorized plotmath expressions via substitute()
> 
> hi all - i've seen versions of this question before, but none seem to get
> directly at my solving my (probably very simple) issue:
> 
> i simply want to annotate the tick marks on an axis with (superscripted)
> 10^x notation, and tried this:
> 
> axis(1, at = axTicks(1), as.expression(substitute(10^foo, list(foo =
> axTicks(1))))
> 
> thinking the as.expression/substitute would create the appropriate
> expression vector from the expansion of the foo vector.
> i'm continually stuck in the error process, however, with axis() where R
> complains that i've only provided a single label.
> i must be missing a function that explicitly "unfolds"(?) the result of the
> substitute() call, without actually evaluating the contents of that call?
> 
> sorry in advance if this is clear in the docs somewhere, though i just
> can't seem to locate it :-/
> 
> cheers and thanks for any pointers!
> 
> -murat
> 
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