[R] Using a number as a name to access a list

[Jan T. Kim]

On Thu, Feb 10, 2005 at 01:35:56PM -0000, michael watson (IAH-C) wrote:

> I have a variable that contains the following numerical text "04010".
> This is the name to access a list:
> 
> > as.list(KEGGPATHID2NAME)$"04010"
> [1] "MAPK signaling pathway"
> 
> Marvellous!  Except I want to do that when "04010" is assigned to a
> variable called path and I can't figure out how to do it!
> 
> > path <- "04010"
> >
> > # the original and best
> > as.list(KEGGPATHID2NAME)$"04010"
> [1] "MAPK signaling pathway"
> >
> > # clearly this doesn't, and shouldn't, work
> > as.list(KEGGPATHID2NAME)$path
> NULL

$ allows only a literal character string or a symbol as the index, according
to the R language definition, but [[ indexing does the same as $ and can
be used for computed indexing. So

    as.list(KEGGPATHID2NAME)[[path]]

should do what you want.

Greetinx, Jan
-- 
 +- Jan T. Kim -------------------------------------------------------+
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