411 REFERENCE · Wikibooks
Linear Algebra and the C Language/a0oe
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The matrix A and the inverse matrix of A have the same eigenvectors but arranged in reverse order
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% Properties of spectral decomposition:
%
% To calculate the spectral decomposition of a symetric matrix A, we need:
%
% b: The columns of the eigenvectors of A
% r: The rows of eigenvectors of the inverse of A
%
% The eigenvectors of the inverse of A are identical to
% the eigenvectors of A but not in the correct order. (Try the example)
%
% To obtain the eigenvector rows of the inverse of A,
% I will take the transpose of the eigenvectors of A,
% since A and the inverse of A have the same eigenvectors,
% only when A is symetric.
clear, clc
A = round(10*randn(3)); %% A matrix 3x3
A = A'*A; %% A symetric matrix
invA = inv(A);
% Eigenvectors, Eigenvalues of A
[AEvectors,AEvalues] = eigs(A);
% Eigenvectors, Eigenvalues of inverse of A
[invAEvectors,invAEvalues] = eigs(invA);
AEvectors
invAEvectors
%%