Re: [R] Summing up matrices in a list

From: Dimitris Rizopoulos <dimitris.rizopoulos_at_med.kuleuven.ac.be>
Date: Thu 17 Mar 2005 - 03:29:00 EST

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


> 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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>



R-help@stat.math.ethz.ch mailing list
https://stat.ethz.ch/mailman/listinfo/r-help PLEASE do read the posting guide! http://www.R-project.org/posting-guide.html Received on Thu Mar 17 03:37:33 2005

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