[R] which() function help page precision

[buzon informatica, ige]

The which() function help page states that, in the default case, what the function returns  is:
" Basically, the result is (1:length(x))[x]."
That would only be true if there are not any NA values in x. I think it would be more accurate to say:
"Basically, the result is (1:length(x))[!is.na(x) & x]."

The "strange" (IMHO) behavior of logical indexing in R makes it necessary to exclude NA values.
For this reason, I  use to wrap logical indices with  which(). I would have written the above expression as:
(1:length(x))[which(x)]
But that would have been a really bad explanation of how the which() function works ;)

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