On 2012-08-28 07:44, Mauricio Cornejo wrote:
William, David, and Peter,
Thank you all so much for your help on this. Though I had read the help files
on 'subset' and '[', I had not been able to discern from that text what the
problem was. I could not have solved it without your help.
The help file on 'subset' mentions "For ordinary vectors, the result is simply x[subset
& !is.na(subset)]." However, since I was dealing with a data frame at the time, I
failed to appreciate the relevance (but I get it now).
I've gone back to read the help on '[' and I still don't see where this functionality is
described. The page has section titled "NAs in indexing", whose content I
interpret as being limited to NAs in the indices (and not in the returned values). I
can't find any text in the documentation describing the subtle behavior you kindly
pointed out.
Hmmm, it seems to me that the page is clear:
"... NA index picks an unknown element and so *returns* NA
in the corresponding element of ..."
(my emphasis)
Isn't that exactly what occurs?
Peter Ehlers
Thanks again,
Mauricio
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