[R] how can I attach a variable stored in

jim holtman jholtman at gmail.com
Thu Sep 20 21:47:13 CEST 2007


try:

attach(get(ls(pat="^foo")))

On 9/20/07, Peter Waltman <waltman at cs.nyu.edu> wrote:
> Hi Mark -
>
> Thanks for the reply.  Sorry I didn't really clarify too well what I'm
> trying to do.  The issue is not that I can't see the variable that gets
> loaded.
>
> The issue is that the variable is a list variable, and I'd like to write
> a function that will take the .RData filename and attach the variable it
> contains so that I can more easily access its contents, i.e.
>
>    foo.bar <- list( "a"= "a", "b"=1 )
>    save( file="foo.bar.RData", foo.bar )
>    rm( foo.bar )
>
>    my.fn <- function( fname ) {
>       load( fname )
>       attach( ls( pat="foo" ) ) #  I want to attach( foo.bar ), but
>    this doesn't work
>    }
>
>    ls()  # prints out "foo.bar"
>
>    attach( ls( ) )   # still doesn't work
>    attach( foo.bar )  # works
>
> So, basically, the question is how can I attach the variable that's
> stored in a file if I don't already know it's name?
>
> Thanks again!
>
> Peter
>
> Leeds, Mark (IED) wrote:
> > I don't think I understand your question but John Fox has written a very
> > nice documentat about scoping and environments on his website.
> > It's probably easy to find the site by googling "John Fox" but, if you
> > can't find it, let me know.
> >
> > As I said, I don't think that I understand your question but, if you
> > loaded a list variable using load("whatever.Rdata"), the variable will
> > just be suitting in  your workspace. You don't need to attach anything
> > because load just loads the data right into the workspace.
> > So typing the variable name should show the data.
> >
> >
> >
> >
> > -----Original Message-----
> > From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-project.org]
> > On Behalf Of Peter Waltman
> > Sent: Thursday, September 20, 2007 1:32 PM
> > To: r-help at r-project.org
> > Subject: [R] how can I attach a variable stored in
> >
> > Hi -
> >
> > Any help would be greatly appreciated.
> >
> > I'm loading a list variable that's stored in an .RData file and would
> > like attach it.
> >
> > I've used attach( <file_name> ), but that only lets me see the variable
> > that's stored in the file.
> >
> > As the variable name is of the form "comp.x.x", I've tried using attach(
> > ls( pat="comp" ) ), but get an error as ls() just gives back a string.
> >
> > I've also played around with eval(), but don't really quite get what
> > that function does since it seems to get into the R internals which I
> > don't entirely understand and I haven't found any great unified
> > documentation on R's handling environment and scoping.
> >
> > Thanks,
> >
> > Peter Waltman
> >
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-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem you are trying to solve?



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