[R] eval(expr) without printing to screen?

[baptiste auguie]

Hi,

What about this,

eval(parse(text=expr))

(no print)

HTH,

baptiste


2009/9/19 Nick Matzke <matzke at berkeley.edu>:
> Hi,
>
> I have a script which I source, which evaluates a changing expression call
> hundreds of times.  It works, but it prints to screen each time, which is
> annoying.  There must be simple way to suppress this, or to use a slightly
> different set of commands, which will be obvious to those wiser than I...
>
>
> Here is a simpler mockup which shows the issue:
>
> x = data.frame(rbind(c(1,2,3),c(1,2,3)))
> xnames = c("a", "b", "c")
> names(x) = xnames
>
> for(i in 1:length(x))
> {
> # Create a varying string expression
> expr = paste("y = x$", xnames[i], "[1]", sep="")
>
> # evaluate expression
> eval(parse(text=print(expr)))
>
> # This command prints the expression to screen even when embedded in a
> function in a sourced script.  I would prefer it didn't!
> }
>
>
> PS: I have to go through this rigamarole:
>
> expr = "y1 = x$c[1]"
> eval(parse(text=print(expr)))
>
> Because the following doesn't work, even though it seems like it should:
> expr = "y = x$c[2]"
> eval(expr)
>
>
>
>
> --
> ====================================================
> Nicholas J. Matzke
> Ph.D. Candidate, Graduate Student Researcher
> Huelsenbeck Lab
> Center for Theoretical Evolutionary Genomics
> 4151 VLSB (Valley Life Sciences Building)
> Department of Integrative Biology
> University of California, Berkeley
>
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>
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>
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>
> Isaac Asimov (1989). "The Relativity of Wrong." The Skeptical Inquirer,
> 14(1), 35-44. Fall 1989.
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>
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