R help - Aug 2009 - Paste symbol and calculation in plot

I'm trying to annotate a density plot and I would like to have R calculate
the
standard deviation and place it in the plot next to the standard deviation
symbol
"sigma". I can successfully use the text command to paste "StDev
=",round(sd(Data),digits=3))
on the plot. However, I have trouble when I want to replace "StDev"
with the Greek
symbol sigma (See code below). 

	set.seed(1)
	Data=rnorm(100)
	plot(density(Data))
	text(2,0.35,paste("StDev =",round(sd(Data),digits=3)))

Through searching the help files I figured out that I can paste the sigma symbol
on the
plot using the command "expression".

	text(2,0.3,expression(paste(sigma," = 0.898")))

However, when I try to paste together the sigma symbol and the standard
deviation
that R is calculating, the text of the command to calculate the standard
deviation
shows up on the plot instead of the number which I am asking it to calculate. 
 
	text(2.2,0.25,expression(paste(sigma," =
",round(sd(Data),digits=3))))

Can someone please point me to a resource that will help me figure this out?

Thank You,

Jonathan

I'm no expert at this but it seems like ?plotmath is saying to do
something like:

text(2,0.35,bquote(sigma==.(mySigma),list('mySigma'=round(sd(Data),digits=3))))


Scott



Scott Sherrill-Mix
Department of Microbiology
University of Pennsylvania
402B Johnson Pavilion
3610 Hamilton Walk
Philadelphia, PA  19104-6076



On Tue, Aug 11, 2009 at 4:00 PM, Jonathan R.
Blaufuss<blaufusj at carleton.edu> wrote:
> I'm trying to annotate a density plot and I would like to have R
calculate the
> standard deviation and place it in the plot next to the standard deviation
symbol
> "sigma". I can successfully use the text command to paste
"StDev =",round(sd(Data),digits=3))
> on the plot. However, I have trouble when I want to replace
"StDev" with the Greek
> symbol sigma (See code below).
>
> ? ? ? ?set.seed(1)
> ? ? ? ?Data=rnorm(100)
> ? ? ? ?plot(density(Data))
> ? ? ? ?text(2,0.35,paste("StDev =",round(sd(Data),digits=3)))
>
> Through searching the help files I figured out that I can paste the sigma
symbol on the
> plot using the command "expression".
>
> ? ? ? ?text(2,0.3,expression(paste(sigma," = 0.898")))
>
> However, when I try to paste together the sigma symbol and the standard
deviation
> that R is calculating, the text of the command to calculate the standard
deviation
> shows up on the plot instead of the number which I am asking it to
calculate.
>
> ? ? ? ?text(2.2,0.25,expression(paste(sigma," =
",round(sd(Data),digits=3))))
>
> Can someone please point me to a resource that will help me figure this
out?
>
> Thank You,
>
> Jonathan
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>