sum
From: Peter Dalgaard BSA [mailto:p.dalgaard at biostat.ku.dk] Barry Rowlingson <B.Rowlingson at lancaster.ac.uk> writes:
Luis Silva wrote:
Dear helpers I have a list where each element is a matrix (the list is obtained with lapply). I want to sum those matrices. Is there a function to do that? The sum function sums all the elements...
Here's a one-liner that converts your list into an array (by unlisting it and then packing into an array with the right three dimensions) and then runs apply(...,c(1,2),sum) to get the
answer you
want:
Didn't someone do an abind() function at some point? (Generalizing cbind/rbind)
I believe there's an abind for Splus on StatLib, if I remember correctly by Tony Plate & Rich Heiberger. Do not believe it was made available for R, though I believe it'd be very useful. [snipped]
However, aren't we ignoring the obvious?: s<-0;(for(a in l)s<-s+a)
Indeed! (I guess somehow the evil of for loops in the old S in deeply
engrained in some of us.) Altough I like Sundar's version, too.
Cheers,
Andy
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