I've played a bit with the problem that Jeff Laake
reported on R-help:
# create data:
jl <- data.frame(x=rep(1, 3), y=tapply(1:9,
rep(c('A','B','C'), each=3),
sum))
jl2 <- jl
jl2$y <- as.numeric(jl2$y)
# do the test:
> tapply(jl$y, jl$x, length)
1
3
> tapply(jl2$y, jl2$x, length)
1
3
> by(jl2$y, jl2$x, length)
jl2$x: 1
[1] 3
> by(jl$y, jl$x, length)
INDICES: 1
[1] 1
The result of 'by' on the 1-dimensional array is
giving the correct answer to a question that I don't
think many of us thought we were asking.
Once upon a time 'by' gave 3 as the answer in both
situations.
'by.default' used to be a one-liner, but now decides
what to do based on 'length(dim(data))'.
This specific problem goes away if the line:
if (length(dim(data)))
is replaced by:
if(length(dim(data)) > 1)
But I don't know what other mischief such a change
would make.
Patrick Burns
patrick at burns-stat.com
+44 (0)20 8525 0696
http://www.burns-stat.com
(home of S Poetry and "A Guide for the Unwilling S User")