You can convert it to an array and then use apply:

> mat1
     [,1] [,2] [,3] [,4]
[1,]    3    2   12    4
[2,]   14   13   13    2
[3,]   15    9    6    9
[4,]    2   15   13   19
> mat2
     [,1] [,2] [,3] [,4]
[1,]    0   11   10    7
[2,]   12    9    3   13
[3,]   -4   13    0   14
[4,]   -2    0   -4   -1
> mat3
     [,1] [,2] [,3] [,4]
[1,]   20    6   16   23
[2,]   24    8   11   12
[3,]   15   13    6   16
[4,]    5   22   20   25
>
> x <- array(c(mat1,mat2,mat3), dim=c(4,4,3))
> apply(x,c(1,2),mean)
          [,1]      [,2]      [,3]     [,4]
[1,]  7.666667  6.333333 12.666667 11.33333
[2,] 16.666667 10.000000  9.000000  9.00000
[3,]  8.666667 11.666667  4.000000 13.00000
[4,]  1.666667 12.333333  9.666667 14.33333


On Mon, May 18, 2009 at 8:40 PM, dxc13 <dxc13@health.state.ny.us> wrote:

>
> useR's,
> I have several matrices of size 4x4 that I want to calculate means of their
> respective positions with.  For example, consider I have 3 matrices given
> by
> the code:
> mat1 <- matrix(sample(1:20,16,replace=T),4,4)
> mat2 <- matrix(sample(-5:15,16,replace=T),4,4)
> mat3 <- matrix(sample(5:25,16,replace=T),4,4)
>
> The result I want is one matrix of size 4x4 in which position [1,1] is the
> mean of position [1,1] of the given three matrices.  The same goes for all
> other positions of the matrix.  If these three matrices are given in
> separate text files, how can I write code that will get this result I need?
>
> Thanks in advance,
> dxc13
> --
> View this message in context:
> http://www.nabble.com/how-to-calculate-means-of-matrix-elements-tp23607694p23607694.html
> Sent from the R help mailing list archive at Nabble.com.
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html<http://www.r-project.org/posting-guide.html>
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?

	[[alternative HTML version deleted]]


