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author Antonio Pino Robles <data.script93@gmail.com>
date Fri, 29 May 2015 09:48:36 +0200
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1 function P = vecperm(m, n)
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2 %VECPERM Vec-permutation matrix.
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3 % VECPERM(M, N) is the vec-permutation matrix, an MN-by-MN
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4 % permutation matrix P with the property that if A is M-by-N then
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5 % vec(A) = P*vec(A').
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6 % If N is omitted, it defaults to M.
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8 % P is formed by taking every n'th row from EYE(M*N), starting with
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9 % the first and working down - see p. 277 of the reference.
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11 % Reference:
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12 % H. V. Henderson and S. R. Searle The vec-permutation matrix,
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13 % the vec operator and Kronecker products: A review Linear and
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14 % Multilinear Algebra, 9 (1981), pp. 271-288.
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16 if nargin == 1, n = m; end
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18 P = zeros(m*n);
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19 I = eye(m*n);
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21 k = 1;
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22 for i=1:n
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23 for j=i:n:m*n
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24 P(k,:) = I(j,:);
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25 k = k+1;
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26 end
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27 end