Dear jim,
Yes.
But, unfortunately, two nested for loops will execute very slow.
It is not very serious problem to do my task with an image
processing package, I am wondering if it is efficiently possible with
R.
Thursday, July 27, 2006, 2:20:13 PM, you wrote:
jh> Is this what you want: the mean of the surrounding 4 cells?
jh>
>> x <- matrix(1:100, 10) # create data
>> rmean <- matrix(0,5,5) # result matrix
>> for (i in 1:5){
jh> + for (j in 1:5){
jh> + rmean[i, j] <- mean(x[c(-1,0) + 2 * i, c(-1,0) + 2 * j])
jh> + }
jh> + }
>> x
jh> [,1] [,2] [,3] [,4] [,5] [,6] [,7] [,8] [,9] [,10]
jh> [1,] 1 11 21 31 41 51 61 71 81 91
jh> [2,] 2 12 22 32 42 52 62 72 82 92
jh> [3,] 3 13 23 33 43 53 63 73 83 93
jh> [4,] 4 14 24 34 44 54 64 74 84 94
jh> [5,] 5 15 25 35 45 55 65 75 85 95
jh> [6,] 6 16 26 36 46 56 66 76 86 96
jh> [7,] 7 17 27 37 47 57 67 77 87 97
jh> [8,] 8 18 28 38 48 58 68 78 88 98
jh> [9,] 9 19 29 39 49 59 69 79 89 99
jh> [10,] 10 20 30 40 50 60 70 80 90 100
>> rmean
jh> [,1] [,2] [,3] [,4] [,5]
jh> [1,] 6.5 26.5 46.5 66.5 86.5
jh> [2,] 8.5 28.5 48.5 68.5 88.5
jh> [3,] 10.5 30.5 50.5 70.5 90.5
jh> [4,] 12.5 32.5 52.5 72.5 92.5
jh> [5,] 14.5 34.5 54.5 74.5 94.5
>>
jh>
jh> On 7/27/06, Vladimir Eremeev <[EMAIL PROTECTED]> wrote:Dear r-help,
jh> I have a matrix, suppose, 10x10, and I need the matrix 5x5, having
jh> in each cell a mean value of the cells from the initial matrix.
jh> Please, point me to a function in R, which can help me doing that.
jh> Digging the documentation and mail archives didn't give me a result.
jh> Thank you.
jh> ---
jh> Best regards,
jh> Vladimir mailto:[EMAIL PROTECTED]
jh> ______________________________________________
jh> [email protected] mailing list
jh> https://stat.ethz.ch/mailman/listinfo/r-help
jh> PLEASE do read the posting guide
jh> http://www.R-project.org/posting-guide.html
jh> and provide commented, minimal, self-contained, reproducible code.
---
Best regards,
Vladimir mailto:[EMAIL PROTECTED]
==========================================================================
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Space Monitoring & Ecoinformation Systems Sector, Moscow, Russia, 119071,
Institute of Ecology, Phone: (095) 135-9972;
Russian Academy of Sciences Fax: (095) 135-9972
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