[R] sum of unknown number of matrices
Berwin A Turlach
berwin at maths.uwa.edu.au
Wed Jun 4 17:33:10 CEST 2008
G'day Shubha,
On Wed, 4 Jun 2008 20:23:35 +0530
"Shubha Vishwanath Karanth" <shubhak at ambaresearch.com> wrote:
> Something like do.call("+",l) is not working...why is this?
Well, as the error message says, "+" is either a unary or a binary
operator, i.e. it takes either one or two arguments, but not more.
> I may not be knowing the number of matrices in the list...
This is perhaps a bit complicated but it works:
R> a=b=c=d=matrix(1:4,2,2)
R> l=list(a,b,c,d)
R> library(abind) ## may have to install this package first
R> apply(do.call(abind, list(l, along=3)), 1:2, sum)
[,1] [,2]
[1,] 4 12
[2,] 8 16
HTH.
Cheers,
Berwin
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