[R] Subset with selection variable from function argument. Is there another way?

[Prof Brian Ripley]

On Wed, 11 May 2005, Fredrik Karlsson wrote:

> Dear list,
>
> I'm making my current code more generic and would like some advise.
> The basic problem is subset and the name of the column to be compared
> for selection.
>
> What I've come up with is
>
>> data(mammals)
>> set <- bottompremolars"
>> subset(mammals, eval(parse(file="",text=set)) > 2)
>
> This seems a bit odd.  Is there a nicer way?

Try

set <- "bottompremolars"
mammals[[set]]

assuming it is a data frame and you just want the one column.

subset() is just a convenience wrapper for the basic indexing operations, 
which are well worth learning.

-- 
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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