R help - May 2007 - stringification magic in subset?

dear R wizards:

I am trying to replace subset() with my own version that first checks
that each name in the select statement has a corresponding name in the
data set.  preferably, it would have the same syntax and semantics as
subset() otherwise.

alas, subset works in interesting ways:

subset(d, select=col1)

works just like

subset(d, select="col1")

somehow, subset manages to "stringify" its argument in such cases.  Is
it possible to duplicate the subset method one-for-one?

a minor question---where do I find the source definition such as that
of subset(), which is defined in
> subset
function (x, ...)
UseMethod("subset")
<environment: namespace:base>
>
any help, as usual, appreciated.

regards,

/ivo

ivo welch said the following on 5/2/2007 8:13 AM:
> dear R wizards:
> 
> I am trying to replace subset() with my own version that first checks
> that each name in the select statement has a corresponding name in the
> data set.  preferably, it would have the same syntax and semantics as
> subset() otherwise.
> 
> alas, subset works in interesting ways:
> 
> subset(d, select=col1)
> 
> works just like
> 
> subset(d, select="col1")
> 
> somehow, subset manages to "stringify" its argument in such
cases.  Is
> it possible to duplicate the subset method one-for-one?
> 
> a minor question---where do I find the source definition such as that
> of subset(), which is defined in
> 
>> subset
> function (x, ...)
> UseMethod("subset")
> <environment: namespace:base>
> 
> any help, as usual, appreciated.
> 
> regards,
> 
> /ivo
> 
> ______________________________________________
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> PLEASE do read the posting guide
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> and provide commented, minimal, self-contained, reproducible code.

Try:

methods("subset")

which will point you to "subset.data.frame". The latter code will
answer
your questions.

HTH,

--sundar

Beautiful.  thank you.  /ivo
> Try:
>
> methods("subset")
>
> which will point you to "subset.data.frame". The latter code will
answer
> your questions.
>
> HTH,
>
> --sundar
>