[R] Question about as.numeric with tclvalue

[Prof Brian Ripley]

It's not clear what is going on here, but one possibility is

> as.numeric("pi")
[1] NA
Warning message:
NAs introduced by coercion

OTOH, "Inf" works for me.

The difference is that 'Inf' is a standard C99 value (like 1.23), whereas 
'pi' is a variable in R.  So if you want to allow expressions you need to 
parse and eval them, something like

inp <- "pi"
assign("a", eval(parse(text=inp)), .GlobalEnv)

As ever, please see the message footer and remember to supply a 
reproducible example.


On Sun, 23 Mar 2008, Erin Hodgess wrote:

> Dear R People:
>
> I have an interactive menu via an Rcmdr extension package which asks
> for lower and upper limit to evaluate.
>
> Typically, I use:
>
> assign("a",as.numeric(tclvalue(lowlim)),envir=.GlobalEnv)
>
> and that's fine.
>
> However, if I try to use pi or Inf or -Inf, I get either coerced NAs or NaN.
>
> Does anyone have any suggestions, please?
>
> Thanks,
> Erin
> PS Happy Easter if you celebrate Easter.
>
>
> --
> Erin Hodgess
> Associate Professor
> Department of Computer and Mathematical Sciences
> University of Houston - Downtown
> mailto: erinm.hodgess at gmail.com
>
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>

-- 
Brian D. Ripley,                  ripley at stats.ox.ac.uk
Professor of Applied Statistics,  http://www.stats.ox.ac.uk/~ripley/
University of Oxford,             Tel:  +44 1865 272861 (self)
1 South Parks Road,                     +44 1865 272866 (PA)
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