R help - Feb 2014 - do calculation within expression(), text in plot

Dear Helpers,
   I would like to add some text to my plot, containing a variable and the
   calculated value for the variable.
   As  I  would  like  to  produce  many  plots,  I hope this can be done
   automatically.
   Unfortunately I can't get R to do the calculation for cor(nou,dak) when I
   use expression()..

   text(0,2.2,expression(paste(r[Pearson],"=", cor(nou,dak) , sep=
" ")),pos=4,
   cex=1.5)

   Is there a command that "stops" expression() so the result is
calculated and
   printed in the plot?
   Thank you in advance,
   Tonja

>    Unfortunately I can't get R to do the calculation for cor(nou,dak)
when I
>    use expression()..
> 
>    text(0,2.2,expression(paste(r[Pearson],"=", cor(nou,dak) ,
sep= " ")),pos=4,
>    cex=1.5)
Use bquote() and its .() operator, as in
  with(mtcars, {
      plot(wt, mpg)
      text(4, 30, bquote(r[Pearson] ~ "=" ~ .(cor(wt, mpg))))
  })

Bill Dunlap
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 Tonja Krueger
> Sent: Friday, February 28, 2014 2:27 AM
> To: r-help at r-project.org
> Subject: [R] do calculation within expression(), text in plot
> 
> 
>    Dear Helpers,
>    I would like to add some text to my plot, containing a variable and the
>    calculated value for the variable.
>    As  I  would  like  to  produce  many  plots,  I hope this can be done
>    automatically.
>    Unfortunately I can't get R to do the calculation for cor(nou,dak)
when I
>    use expression()..
> 
>    text(0,2.2,expression(paste(r[Pearson],"=", cor(nou,dak) ,
sep= " ")),pos=4,
>    cex=1.5)
> 
>    Is there a command that "stops" expression() so the result is
calculated and
>    printed in the plot?
>    Thank you in advance,
>    Tonja
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