[R] Use of variables to reference to objects

[Thomas Lumley]

On Fri, 22 Nov 2002, Kris Nackaerts wrote:

> Hi,
>
> I'm new to R and looking for a way to use a variable to reference to an
> object.
>
> I'm plotting several graphs on top of each other and want to do this by
> a for loop. The field I want to graph have names like a1,a2,a3, ...
> I can't figure out how to get this working:
>
> It should look like this:
> lines(spectral$Wavelength,paste("spectral$a",j,sep=""),col=j)
>
> but the "paste()" does not seem to work in this context.
>

No, it wouldn't.  That gives you the name of the variable, not the
variable.

Probably the simplest solution is either
   lines(spectral$Wavelength, spectral[[paste("a",j,sep="")]],col=j)
but there's also
   lines(spectral$Wavelength,get(paste("spectral$a",j,sep="")),col=j)
and various others

	-thomas

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