[R] Double expressions in plot labels

[David Winsemius]

On Jan 22, 2012, at 10:39 PM, Marcin Kozak wrote:

> Hi all,
>
> I wanted to do something of this sort:
>
> library(lattice)
> label <- expression(alpha)
> xx <- substitute(expression(lab %+-% type), list(lab = label, type =  
> " type"))
> stripplot(Species ~ jitter(Petal.Length), iris, ylab = xx,  
> horizontal=T)

Try instead:

label <- quote(alpha)
xx <- substitute(expression(lab %+-% type), list(lab = label, type = "  
type"))
stripplot(Species ~ jitter(Petal.Length), iris, ylab = xx, horizontal=T)

When you nest an expression call inside an expression things do not go  
well.
And quote(alpha) is not the same as "alpha".
>
> (The example plot itself does not make much sense, but I need only to
> construct the label.) Since I want to make it a general function, I
> need to have both these expressions (the "lab" and "type" arguments
> sometimes are and other times are not expressions, but I must assume
> such a possibility). Unfortunately, the above code does not work, that
> is, does not produce a label that should say "alpha +- type" [alpha in
> Greek]. The first part (the alpha) is ignored at all. Any idea how to
> do that?
>
> I work with R 12.1, Windows 7.
>
> Best wishes,
> Marcin
>
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David Winsemius, MD
West Hartford, CT