MATLAB: Matrix formation from two given matrix

matrix manipulation

i want to form a diagonal matrix from two matrix, one contains the value of diagonal elements and other contains how many times it should occur.For example: a=[5 10 15] and b=[2 2 2] so the resultant matrix should look like r=[5 0 0 0 0 0;0 5 0 0 0 0;0 0 10 0 0 0;0 0 0 10 0 0;0 0 0 0 15 0;0 0 0 0 0 15]; But the problem is a and b can vary depending upon the situation or user input.

can i form such a matrix? I will highly appreciate any kind of suggestion.

Thanks, Mamun

Best Answer

"for" loop around repmat() in order to build the diagonal vector, and then diag() that.

Or just use a nested "for" loop.

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MATLAB: Average distance of nonzero diagonal to the main diagonal for sparse matrix

In your example, you do not need to check the diagonals at all, just the first row and column of the matrix!

A = [0 5 0 1 0 0 ;
     0 0 6 0 2 0 ;
     2 0 0 4 0 3 ;
     1 4 0 0 8 0 ;
     0 2 5 0 0 9 ]
ix = [find(A(1,:)) find(A(:,1))']
result = mean(ix-1)

If your definition of non-zero diagonals is that at least one element of the diagonal is non-zero, this might not work. Then you should check

A = [0 0 0 1 0 0 ;
     0 0 6 0 2 0 ;
     0 0 0 4 0 3 ;
     1 4 0 0 8 0 ;
     0 2 5 0 0 9 ]
d = -size(A,1):size(A,2)
q = arrayfun(@(k) any(diag(A,k)>0), d)
d2 = d(q)
result = mean(abs(d2))

MATLAB: How to display in one variable the max of each one of two arrays

c = [max(a) max(b)];

Best Answer

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MATLAB: Average distance of nonzero diagonal to the main diagonal for sparse matrix

MATLAB: How to display in one variable the max of each one of two arrays

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