Matrix logarithm of QT matrices

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The function logm evaluates the matrix logarithm using inverse scaling and squaring, and a Padè approximant.

Contents

Syntax

X = logm(A)

Example

For the logarithm to be well-defined, we need to avoid negative real eigenvalues; here, we choose a positive definite matrix, and check that the matrix exponential of the outcome of logm is again the original matrix.

A = cqt([ 3 1 ], [ 3 1 ]);
L = logm(A);
res = norm(expm(L) - A) / norm(A)

res =

   3.0031e-11