On 11/25/2010 10:30 AM, Peter Ehlers wrote:
On 2010-11-25 07:06, statmobile wrote:
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?
You could use the abind function in the abind package to
convert your list to a 3d array and then use apply on that:
require(abind)
xa <- abind(x, along=3)
apply(xa, 1:2, mean, trim=0.3)
This is exactly what I was seeking, thank you Peter & Dimitris.
Peter Ehlers
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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