[R] Summing up matrices in a list

[John Fox]

Dear Mark,

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
Canada L8S 4M4
905-525-9140x23604
http://socserv.mcmaster.ca/jfox 
-------------------------------- 

> -----Original Message-----
> From: r-help-bounces at stat.math.ethz.ch 
> [mailto:r-help-bounces at 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
> 
> See ?do.call for more information.
> 
> HTH,
> 
> Marc Schwartz
> 
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