arrays - The fastest way to set up sparse matrix in matlab -

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i working iterative methods, , large sparse matrices. instance, want set matrix this:

1   1   0   0   1   0   0   0   0   0 1   1   1   0   0   1   0   0   0   0 0   1   1   1   0   0   1   0   0   0 0   0   1   1   1   0   0   1   0   0 1   0   0   1   1   1   0   0   1   0 0   1   0   0   1   1   1   0   0   1

so diagonals non-zero. in programming, working larger matrix sizes, idea same: few diagonals non-zero, other entries zeros.

i know, how in loop, seems not effective, if matrix size large. work symmetric matrices. appreciate, if provide me code sample matrix along description.

you want spdiags:

m = 6;                       %// number of rows n = 10;                      %// number of columns diags = [-4 -1 0 1 4];       %// diagonals filled = spdiags(ones(min(m,n), numel(diags)), diags, m, n);

this gives:

>> full(a) ans =      1     1     0     0     1     0     0     0     0     0      1     1     1     0     0     1     0     0     0     0      0     1     1     1     0     0     1     0     0     0      0     0     1     1     1     0     0     1     0     0      1     0     0     1     1     1     0     0     1     0      0     1     0     0     1     1     1     0     0     1

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