Unless I'm missing something, all you need to do is create the large matrix and then replace the submatrix via subscripting the rows and columns:
ans <- matrix(0, n, n) sub.seq <- floor(n/2 + 1):n ans[sub.seq, sub.seq] <- submatrix
Patrick Burns
Burns Statistics [EMAIL PROTECTED] +44 (0)20 8525 0696 http://www.burns-stat.com (home of S Poetry and "A Guide for the Unwilling S User")
Doran, Harold wrote:
Dear List:
I am having some difficulty constructing a matrix that must take a specific form. The matrix must be have a lower block of non-zero values and the rest must all be zero. For example, if I am building an n X n matrix, then the first n/2 rows need to be zero and the first n/2 columns must remain as zero with all other elements having a non-zero value that I specify.
For example, assume I start with the following 4 x 4 matrix:
vl.mat <- matrix(0,4,4)
[,1] [,2] [,3] [,4] [1,] 0 0 0 0 [2,] 0 0 0 0 [3,] 0 0 0 0 [4,] 0 0 0 0
I need for the for the first two columns (4/2) to remain as zero and the first two rows (4/2) to remain as zeros. But I need for the bottom block to include some values that I specify.
[,1] [,2] [,3] [,4] [1,] 0 0 0 0 [2,] 0 0 0 0 [3,] 0 0 100 100 [4,] 0 0 100 100
I know that if I use the following I can build a matrix with values along the diagonals where I need them, but I need for the lower block of off-diagonals to also be the same value.
vl.mat <- matrix(0,4,4) vl.mat[(col(vl.mat)%%4 == row(vl.mat)%%4)&col(vl.mat)%%4 !=1 &col(vl.mat)%%4 !=2 ] <- 100
Can anyone offer a suggestion? Thank you.
-Harold
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