R help - Mar 2006 - numerical values in expressions

Hi there, 

I fitted a curve to some data and want to write the equation of the
fitted curve in the figure legend. If I write 

paste(format(fitZ$estimate[1], digits=2), "e^",
format(fitZ$estimate[2],
digits=2), "x +", format(fitZ$estimate[3], digits=2))

i get unformatted output, writing "e^-0.0039x" instead of superposing
the exponent. I tried several variants of "expression", but finally
only
the explicit one 

expression(0.061 * e^"-0.0039x" + 0.010)

where I have to provide the values myself worked. Is there any way to
use the "expression" function to reference actual values of variables
instead of just outputting their names?

Thanks,

Stephan

Stephan Lorenzen wrote:
> Hi there, 
> 
> I fitted a curve to some data and want to write the equation of the
> fitted curve in the figure legend. If I write 
> 
> paste(format(fitZ$estimate[1], digits=2), "e^",
format(fitZ$estimate[2],
> digits=2), "x +", format(fitZ$estimate[3], digits=2))
> 
> i get unformatted output, writing "e^-0.0039x" instead of
superposing
> the exponent. I tried several variants of "expression", but
finally only
> the explicit one 
> 
> expression(0.061 * e^"-0.0039x" + 0.010)
> 
> where I have to provide the values myself worked. Is there any way to
> use the "expression" function to reference actual values of
variables
> instead of just outputting their names?

See the article "R Help Desk: Automation of Mathematical Annotation in 
Plots" in R News 2(3).

Example for this case:

  a <- format(fitZ$estimate[1], digits=2)
  b <- format(fitZ$estimate[2], digits=2)
  d <- format(fitZ$estimate[3], digits=2)

  plot(1:10, main = substitute(a * e^b * x + d,
                               list(a=a, b=b, d=d)))



Uwe Ligges
> Thanks,
> 
> Stephan
> 
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