Applying function to elements of matrices in a list
On 11/25/2010 09:44 AM, Dimitris Rizopoulos wrote:
try this:
Reduce("+", x) / length(x)
Thanks Dimitris, that's very slick, I was unaware of this Reduce function. The issue, is that I actually wanted to do a trimmed mean, and if things prove possible even the median. Is there a way to apply a generic function in the manner I described? Thanks, Brian
Best, Dimitris On 11/25/2010 3:42 PM, statmobile wrote:
Hello R-help, Please cc me on all responses, as I only receive summary emails from this list. I'm wondering if anybody has any tips on how to accomplish this efficiently. I have a list of matrices, and I'm trying to get the mean of the [i,j]'th element of each matrix in a list. So if I have a list of matrices, say x <- list(a=matrix(rnorm(4),nrow=2),b=matrix(rnorm(4),nrow=2)) How would I get a 2x2 matrix, where the i,j'th element would be the mean across the the list of each of the i,j'th elements in the list? That is, where the [1,2] element would be the average of a[1,2] and b[1,2]. Of course my list and matrices are much larger, and I was hoping there would be some trick with lapply that I may be missing here. Thanks, Brian
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