Thomas Lumley wrote:
On Tue, 31 May 2005, Duncan Murdoch wrote:
Mäkinen Jussi wrote:
Dear All,
I luckily found the following feature (or problem) when tried to apply
ifelse-function to an ordered data.
test <- c(TRUE, TRUE, TRUE, FALSE, FALSE, FALSE, FALSE)
ifelse(test, 0, 1:4)
[1] 0 0 0 4 1 2 3
<snippage>
As Dimitris said, this is just recycling. I think getting rid of recycling
on vectors with length greater than 1 would have been a good decision in S
about 15 years ago, but it's too late now.
It wouldn't help the original poster, though. I agree that 0,0,0,4,1,2,3
is a slightly weird result, but I can't think of any reasonable model for
the behaviour of ifelse() that would give any other result except an error
message. [or 0,NA,NA,4,NA,NA,NA, I suppose].
I would vote for the error message. I can't think of a single example
where a vector of length 7 is needed, and a vector of length 4 is
recycled to give it, that *doesn't* give a slightly weird result.
Maybe this is something that should have been changed in R 2.0.0; we
squandered that change from 1.x.x to 2.x.x.
Duncan Murdoch
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