use 'filter':
> x <- matrix(1:100,10)
> 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
> (y <- apply(x, 2, filter, c(1,1,1)))
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] NA NA NA NA NA NA NA NA NA NA
[2,] 6 36 66 96 126 156 186 216 246 276
[3,] 9 39 69 99 129 159 189 219 249 279
[4,] 12 42 72 102 132 162 192 222 252 282
[5,] 15 45 75 105 135 165 195 225 255 285
[6,] 18 48 78 108 138 168 198 228 258 288
[7,] 21 51 81 111 141 171 201 231 261 291
[8,] 24 54 84 114 144 174 204 234 264 294
[9,] 27 57 87 117 147 177 207 237 267 297
[10,] NA NA NA NA NA NA NA NA NA NA
> y[-c(1, nrow(y)),]
[,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
[1,] 6 36 66 96 126 156 186 216 246 276
[2,] 9 39 69 99 129 159 189 219 249 279
[3,] 12 42 72 102 132 162 192 222 252 282
[4,] 15 45 75 105 135 165 195 225 255 285
[5,] 18 48 78 108 138 168 198 228 258 288
[6,] 21 51 81 111 141 171 201 231 261 291
[7,] 24 54 84 114 144 174 204 234 264 294
[8,] 27 57 87 117 147 177 207 237 267 297
>
On 1/30/06, Camarda, Carlo Giovanni <[EMAIL PROTECTED]> wrote:
>
> Dear R-users,
> I'm struggling in R in order to "squeeze" a matrix without using a
> for-loop.
> Although my case is a bit more complex, the following example should
> help you to understand what I would like to do, but without the slow
> for-loop.
> Thanks in advance,
> Carlo Giovanni Camarda
>
>
> A <- matrix(1:54, ncol=6) # my original matrix
> A.new <- matrix(nrow=3, ncol=6) # a new matrix which I'll fill
> # for-loop
> for(i in 1:nrow(A.new)){
> B <- A[i:(i+2), ] # selecting the rows
> C <- apply(B,2,sum) # summing by columns
> A.new[i,] <- C # inserting in the new matrix
> }
>
>
> +++++
> This mail has been sent through the MPI for Demographic Rese...{{dropped}}
>
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--
Jim Holtman
Cincinnati, OH
+1 513 247 0281
What the problem you are trying to solve?
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