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matlabmatrixdeterminants
user215721
user215721

Reputation: 317

Given LUP decomposition of a matrix, how to find determinant in MATLAB?

I want to compute the determinant of a matrix from its LUP decomposition in MATLAB. The determinant can be found from the formula:

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P is a permutation matrix and S is the number of exchanges of rows needed to transform P into an identity matrix. How can I find S in the above formula in MATLAB? Does it have any pre-defined functions, etc.?

Upvotes: 2

Views: 777

Answers (1)

Jonas
Jonas

Reputation: 74940

If you interpret P as an adjacency matrix, and the vector cycles contains the length of all cycles in the graph described by P, then S=sum(cycles) - length(cycles).

Now all is left is to find the length of all the cycles, for which there are several functions on the File Exchange, like this one.

BTW: [L, U, P] = lu(A), and det(A) = det(inv(P))*det(L)*det(U)

Upvotes: 3

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