R help - Jun 2007 - legend + expression

Dear all;

A simple? question.

I'm having a problem with a math expression in the legend of a plot
and I haven't found the way to get this to work, so any help will be
appreciate. Basically I want to include in the plot is the R-squared
and its numerical value, so I tried this:

R2c<-0.82879 # R-squared of calibration model
plot(1:10,1:10)
legend("topleft", legend=c(expression(R[c]^2==format(R2c,nsmall=2))))

Thanks for any hint

PM

what about

legend("topleft",
        legend = bquote( R[c]2 == .(format(R2c,nsmall=2)) )
       )

HTH,
 Peter

On Fri, 2007-06-08 at 17:27 -0400, Pedro Mardones wrote:
> Dear all;
> 
> A simple? question.
> 
> I'm having a problem with a math expression in the legend of a plot
> and I haven't found the way to get this to work, so any help will be
> appreciate. Basically I want to include in the plot is the R-squared
> and its numerical value, so I tried this:
> 
> R2c<-0.82879 # R-squared of calibration model
> plot(1:10,1:10)
> legend("topleft",
legend=c(expression(R[c]^2==format(R2c,nsmall=2))))
> 
> Thanks for any hint
> 
> PM
Try this:

  R2c <- 0.82879

  plot(1:10,1:10)

  R2c.2 <- sprintf("%.2f", R2c)

  legend("topleft", legend = bquote(R[c]^2 == .(R2c.2)))


See ?bquote and if you search the list archives, there are more complex
examples of using 'plotmath' in legends.

Note also that 'nsmall' in format() does not fix the number of digits
after the decimal:
> format(0.82879, nsmall = 2)
[1] "0.82879"

See ?formatC and ?sprintf for better options.

HTH,

Marc Schwartz