try this:
matSums <- function(lis, na.rm=FALSE){
if(!is.list(lis) || !all(sapply(lis, is.matrix))) stop("'lis' must be a list containing 2-dimensional arrays")
dims <- sapply(lis, dim)
n <- dims[1, 1]
p <- dims[2, 1]
if(!all(n == dims[1, ]) || !all(p == dims[2, ])) stop("the matrices must have the same dimensions")
mat <- matrix(unlist(lis), n * p, length(lis))
matrix(rowSums(mat, na.rm=na.rm), n, p)
}
#########
mylist <- list(matrix(1:6, 2), matrix(7:12, 2))
matSums(mylist)
I hope it helps.
Best, Dimitris
---- Dimitris Rizopoulos Ph.D. Student Biostatistical Centre School of Public Health Catholic University of Leuven
Address: Kapucijnenvoer 35, Leuven, Belgium Tel: +32/16/336899 Fax: +32/16/337015 Web: http://www.med.kuleuven.ac.be/biostat/ http://www.student.kuleuven.ac.be/~m0390867/dimitris.htm
----- Original Message ----- From: "Vicky Landsman" <[EMAIL PROTECTED]>
To: <r-help@stat.math.ethz.ch>
Sent: Wednesday, March 16, 2005 5:21 PM
Subject: [R] Summing up matrices in a list
Dear all, I think that my question is very simple but I failed to solve it. I have a list which elements are matrices like this:
mylist[[1]] [,1] [,2] [,3] [1,] 1 3 5 [2,] 2 4 6
[[2]] [,1] [,2] [,3] [1,] 7 9 11 [2,] 8 10 12
I'd like to create a matrix M<-mylist[[1]]+mylist[[2]] [,1] [,2] [,3] [1,] 8 12 16 [2,] 10 14 18
Is there a way to create M without looping? Thanks a lot, Vicky Landsman. [[alternative HTML version deleted]]
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