On Apr 22, 2011, at 12:13 PM, Christine SINOQUET wrote:
Hello,
mat1 only consists of 0s and 1s:
0 0 1 0 0 0
1 1 0 1 1 0
1 1 1 0 1 0
0 1 1 0 0 1
1 0 0 1 0 0
0 1 0 1 0 1
N = 3
M = 6
I would like to "compress" mat1 every two rows, applying summation
over the two rows (per column), at each step, to yield:
mat2
1 1 1 1 1 0
1 2 2 0 1 1
1 1 0 2 0 1
> mat[seq(1, nrow(mat), by=2), ]+mat[seq(2, nrow(mat), by=2), ]
[,1] [,2] [,3] [,4] [,5] [,6]
[1,] 1 1 1 1 1 0
[2,] 1 2 2 0 1 1
[3,] 1 1 0 2 0 1
Then, in mat2, I shall have to count the number of 0s, 1s and 2s,
per column, which is my final aim.
I am aware of possibilities such as
counts <- sapply(mat2,2,fun1)
but I do not know how to write fun1.
Besides, it was perhaps not necessary to waste memory producing the
temporary matrix mat2.
Can somebody help ?
I thank you in advance for your answer.
Best regards,
Christine Sinoquet
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David Winsemius, MD
West Hartford, CT
______________________________________________
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PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
and provide commented, minimal, self-contained, reproducible code.
