Note that according to ?ave, the first argument of ave(), 'x' should be
a *numeric* vector. In your case 'x' is not numeric, it is a character
vector. So I think that ave() works as documented, i.e., if you supply
as first argument a numeric vector, then you do get as an output a
numeric vector.
Best,
Dimitris
brenb...@brenbarn.net wrote:
Full_Name: Brendan Barnwell
Version: 2.9.0
OS: Windows XP Pro
Submission from: (NULL) (71.102.131.29)
The ave() function returns an incorrect datatype. Specifically, ave(x, g, f)
always returns a vector with the same mode as x, rather than using the mode of
the vector returned by f. Observe:
x
[1] "A" "B" "C" "A" "B" "C" "A" "B" "C" "A" "B" "C" "A" "B" "C" "A" "B" "C" "A"
"B" "C" "A" "B" "C" "A" "B" "C" "A" "B" "C"
g
[1] "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X"
"Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y" "X" "Y"
ave(x, g, FUN=length)
[1] "15" "15" "15" "15" "15" "15" "15" "15" "15" "15" "15" "15" "15" "15" "15"
"15" "15" "15" "15" "15" "15" "15" "15" "15"
[25] "15" "15" "15" "15" "15" "15"
Even though the length() function returns a vector of integers, ave()
inappropriately converts this to a character vector. The bug is due to this
line in the definition of ave():
split(x, g) <- lapply(split(x, g), FUN)
By sticking the result of the lapply back into the original argument x, it
coerces that result to the type of that argument. This contradicts the
documentation, which says that the value of ave() is "a numeric vector". I
would suggest that this documentation itself doesn't describe the desired
behavior. The result vector should be of the type returned by FUN (just as it
is for tapply). Otherwise it is impossible to use ave() to compute summary
statistics whose type differs from that of the argument.
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Dimitris Rizopoulos
Assistant Professor
Department of Biostatistics
Erasmus University Medical Center
Address: PO Box 2040, 3000 CA Rotterdam, the Netherlands
Tel: +31/(0)10/7043478
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