System: R 1.9.1 on Windows 2000.
Description of problem:
So far as I can tell, this occurs only when using apply() on an array of
dimension >=3 AND when for each iteration the function returns a named
vector of length >=2. I propose the source of the bug and the fix below,
but let me stick to the facts first.
Here is an example:
>a<-array(1:24, dim=2:4)
> func1<-function(x)c(a=mean(x),b=max(x))
> func2<-function(x)c(mean(x),max(x))
> apply(a,1:2,func1)
Error in array(ans, c(len.a%/%d2, d.ans), if (is.null(dn.ans)) { :
length of dimnames [2] must match that of dims
[3]> apply(a,1:2,func2)
, , 1
[,1] [,2]
[1,] 10 11
[2,] 19 20
, , 2
[,1] [,2]
[1,] 12 13
[2,] 21 22
, , 3
[,1] [,2]
[1,] 14 15
[2,] 23 24
******************
The problem appears to be in the next to last line of apply in the
"list" construction
if (len.a > 0 && len.a%%d2 == 0)
return(array(ans, c(len.a%/%d2, d.ans), if (is.null(dn.ans)) {
if (!is.null(ans.names)) *****list(ans.names, NULL) ****
} else c(list(ans.names), dn.ans)))
return(ans)
}
As the error message says, the dimnames list is the wrong length. I
believe the following change fixes the problem, though someone much more
familiar with the code will need to check and/or improve it:
if (len.a > 0 && len.a%%d2 == 0)
return(array(ans, c(len.a%/%d2, d.ans), if (is.null(dn.ans)) {
if (!is.null(ans.names))
*****c(list(ans.names),vector(mode="list",length(d.ans))) *****
} else c(list(ans.names), dn.ans)))
return(ans)
}
With this change, both my examples (and others) ran fine.
I checked the bug list and didn't find this problem, but if I just
missed it, I apologize for wasting your time. While I am here, let me
again take the opportunity to say that I continue to be amazed by the R
phenomenon. I appreciate the hard work that you all do, and I am
astounded by the patience you display on R-help answering questions from
people who for reasons I cannot fathom, won't read the excellent
documentation that you all have written. Sometimes I get exasperated
just reading the questions, let alone answering them.
Cheers,
Bert Gunter
Genentech
