[R] A suggestion to improve ifelse behaviour with vector yes/no arguments

[Thomas Lumley]

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].

 	-thomas