411 REFERENCE · Wikibooks
Linear Algebra and the C Language/a0oh
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b1r1**2 = b1r1; ... ... ... b1r1**3 = b1r1; ... ... ... b1r1**P = b1r1;
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% A property of spectral decomposition:
%
% The b*r* are projectors. For example, if I project point P onto the x-axis,
% P is on the x-axis. Once P is on the x-axis, I can project it an infinite
% number of times onto the x-axis, and it will not move.
% This is materialized in our case by the fact :
%
% b1r1**2 = b1r1
% b1r1**3 = b1r1
% b1r1**4 = b1r1
% ...
% b1r1**n = b1r1
%
% V (b) : The columns of the eigenvectors of A
% V'(r) : The rows of the eigenvectors of the inverse of A
% (Here the transpose: see the first example).
%
% V1V1' (b1r1) is obtained by multiplying the first column of the eigenvector
% of A by the first row of the eigenvector of the inverse of A
clear, clc
A = round(10*randn(3)); %% A matrix 3x3
A = A'*A; %% A symetric matrix
% Eigenvectors, Eigenvalues
[Evectors,Evalues] = eigs(A);
V1 = Evectors(:,1);
V2 = Evectors(:,2);
V3 = Evectors(:,3);
b1r1_2 = (V1*V1')^2
b1r1_4 = (V1*V1')^4
b1r1_6 = (V1*V1')^6
%%