Is this what you want: the mean of the surrounding 4 cells?

> x <- matrix(1:100, 10)  # create data
> rmean <- matrix(0,5,5)  # result matrix
> for (i in 1:5){
+     for (j in 1:5){
+         rmean[i, j] <- mean(x[c(-1,0) + 2 * i, c(-1,0) + 2 * j])
+     }
+ }
> x
      [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
 [1,]    1   11   21   31   41   51   61   71   81    91
 [2,]    2   12   22   32   42   52   62   72   82    92
 [3,]    3   13   23   33   43   53   63   73   83    93
 [4,]    4   14   24   34   44   54   64   74   84    94
 [5,]    5   15   25   35   45   55   65   75   85    95
 [6,]    6   16   26   36   46   56   66   76   86    96
 [7,]    7   17   27   37   47   57   67   77   87    97
 [8,]    8   18   28   38   48   58   68   78   88    98
 [9,]    9   19   29   39   49   59   69   79   89    99
[10,]   10   20   30   40   50   60   70   80   90   100
> rmean
     [,1] [,2] [,3] [,4] [,5]
[1,]  6.5 26.5 46.5 66.5 86.5
[2,]  8.5 28.5 48.5 68.5 88.5
[3,] 10.5 30.5 50.5 70.5 90.5
[4,] 12.5 32.5 52.5 72.5 92.5
[5,] 14.5 34.5 54.5 74.5 94.5
>



On 7/27/06, Vladimir Eremeev <wl@eimb.ru> wrote:
>
> Dear r-help,
>
> I have a matrix, suppose, 10x10, and I need the matrix 5x5, having
> in each cell a mean value of the cells from the initial matrix.
>
> Please, point me to a function in R, which can help me doing that.
>
> Digging the documentation and mail archives didn't give me a result.
>
> Thank you.
>
> ---
> Best regards,
> Vladimir                mailto:wl@eimb.ru
>
> ______________________________________________
> R-help@stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> 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 you are trying to solve?

	[[alternative HTML version deleted]]

