# RE: [R] Summing up matrices in a list

From: John Fox <jfox_at_mcmaster.ca>
Date: Thu 17 Mar 2005 - 04:00:27 EST

I believe that your solution won't work if there are more than two matrices to sum.

Regards,
John

John Fox
Department of Sociology
McMaster University
Hamilton, Ontario
905-525-9140x23604
http://socserv.mcmaster.ca/jfox

> -----Original Message-----
> From: r-help-bounces@stat.math.ethz.ch
> [mailto:r-help-bounces@stat.math.ethz.ch] On Behalf Of Marc Schwartz
> Sent: Wednesday, March 16, 2005 11:30 AM
> To: Vicky Landsman
> Cc: R-Help
> Subject: Re: [R] Summing up matrices in a list
>
> On Wed, 2005-03-16 at 18:21 +0200, Vicky Landsman wrote:
> > 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,
>
>
> > do.call("+", mylist)
> [,1] [,2] [,3]
> [1,] 8 12 16
> [2,] 10 14 18
>
>
> HTH,
>
> Marc Schwartz
>
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