[R] sum of unknown number of matrices

[Dimitris Rizopoulos]

try a simple for loop, it will be fast enough in this case, e.g.,

matSums <- function (lis) {
    out <- array(data = 0, dim = dim(lis[[1]]))
    for (i in seq(along = lis))
        out <- out + lis[[i]]
    out
}

a <- b <- c <- d <- matrix(1:4, 2, 2)
l <- list(a, b ,c, d)

matSums(l)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Shubha Vishwanath Karanth" <shubhak at ambaresearch.com>
To: <r-help at stat.math.ethz.ch>
Sent: Wednesday, June 04, 2008 4:53 PM
Subject: [R] sum of unknown number of matrices


> Hi R,
>
>
>
> I have a list of matrices. I need to get the sum of all the matrices 
> in
> the list.
>
>
>
> Example:
>
> a=b=c=d=matrix(1:4,2,2)
>
> l=list(a,b,c,d)
>
>
>
>
>
> I need:
>
>> a+b+c+d
>
>     [,1] [,2]
>
> [1,]    4   12
>
> [2,]    8   16
>
>
>
> Something like do.call("+",l) is not working...why is this?
>
>
>
>
>
> I may not be knowing the number of matrices in the list...
>
>
>
> Thanks, Shubha
>
>
>
> This e-mail may contain confidential and/or privileged 
> i...{{dropped:13}}
>
> ______________________________________________
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> PLEASE do read the posting guide 
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> and provide commented, minimal, self-contained, reproducible code.
> 


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