Re: [R] Variable passed to function not used in function in select=... in subset

From: Gabor Grothendieck <>
Date: Mon, 10 Nov 2008 17:08:41 -0500

On Mon, Nov 10, 2008 at 4:17 PM, Wacek Kusnierczyk <> wrote:
> Gabor Grothendieck wrote:
>> Certainly this has been recognized as a potential problem:
>> however, it is convenient when you are performing
>> an analysis and entering commands directly as opposed
>> to writing a program although possibly the potential ambiguities
>> overshadow the convenience.
> in most cases, i do not see why one could not use a string literal
> passed by value instead of having an expression deparsed within the
> function, which may lead to confusing behaviour. this would give much
> more consistent and predictable code. this has nothing to do with the
> evaluation mechanism, which can still be lazy.
> in the case of subset, i do not really see how this design might be
> helpful, but it's easy to see how it can be harmful, examples have just

I think the thrust of your comments were already made by reference.

Regarding the convenience it occurs in expressions like this:

   iris2 <- subset(iris, select = - Species)

to create a data frame without the Species column.

Perhaps this would have better been done by allowing an optional formula for the select clause:

   iris2 <- subset(iris, select = ~ - Species)

but I think R is stuck with what it has due to compatibility and the large base of users yet its still possible to add functions in packages or new functions to R so a new variant of subset would be possible in which case one could decide to use the new function in place of the old one. mailing list PLEASE do read the posting guide and provide commented, minimal, self-contained, reproducible code. Received on Mon 10 Nov 2008 - 22:17:31 GMT

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