Thanks Uwe.  I think your recipe is substantially sexier than mine.

However I will, I believe, ***NEVER*** understand how to put together
plotmath constructs.  They seem to require some subset of:

    * expression()
    * bquote()
    * substitute()
    * parse()
    * paste()
    * as.expression()
    * .(...)

(and quite possibly other things that I have forgotten) in a bewildering
variety of combinations with no perceptible rationale as what combination
is required in what circumstances.

It makes quantum mechanics look simple by comparison.

    cheers,

        Rolf

On 06/10/12 06:58, Uwe Ligges wrote:


On 05.10.2012 09:30, Rolf Turner wrote:

I want to do something like:

TH <- sprintf("%1.1f",c(0.3,0.5,0.7,0.9,1))
plot(1:10)
legend("bottomright",pch=1:5,legend=parse(text=paste("theta ==",TH)))

Notice that the final "1" comes out in the legend as just plain "1" and NOT
as "1.0" although TH is

[1] "0.3" "0.5" "0.7" "0.9" "1.0"

I can get plotmath to preserve "1.0" as "1.0" and NOT convert it to "1"
if I use substitute, as in

text(2,5,labels=substitute(list(theta == a),list(a=TH[5])))

but substitute doesn't work appropriately with vectors.

Can anyone tell me how to get a "1.0" rather than "1" in the legend?

Ta.

     cheers,

         Rolf Turner

P.S. Just figured out a way using sapply():

leg <- sapply(TH,function(x){substitute(list(theta == a),list(a=x))})
plot(1:10)
legend("bottomright",pch=1:5,legend=parse(text=leg))

Note that the use of "parse" (pace Thomas Lumley! :-) ) is required ---
"legend=leg" does NOT work.

Getting here required an enormous amount of trial and error. And it seems
pretty kludgy.

Is there a sexier way?


Not sure what is sexier here. I'd stay with

leg <- lapply(TH, function(x) bquote(list(theta == .(x))))
plot(1:10)
legend("bottomright", pch=1:5, legend=as.expression(leg))


Best,
Uwe Ligges




         R. T.

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