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Create local repository for matrix toolboxes. Step #0 done.
author Antonio Pino Robles <data.script93@gmail.com>
date Wed, 06 May 2015 14:56:53 +0200
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8f23314345f4 Create local repository for matrix toolboxes. Step #0 done.
Antonio Pino Robles <data.script93@gmail.com>
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1 function C = comp(A, k)
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2 %COMP Comparison matrices.
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3 % COMP(A) is DIAG(B) - TRIL(B,-1) - TRIU(B,1), where B = ABS(A).
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4 % COMP(A, 1) is A with each diagonal element replaced by its
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5 % absolute value, and each off-diagonal element replaced by minus
8f23314345f4 Create local repository for matrix toolboxes. Step #0 done.
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6 % the absolute value of the largest element in absolute value in
8f23314345f4 Create local repository for matrix toolboxes. Step #0 done.
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7 % its row. However, if A is triangular COMP(A, 1) is too.
8f23314345f4 Create local repository for matrix toolboxes. Step #0 done.
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8 % COMP(A, 0) is the same as COMP(A).
8f23314345f4 Create local repository for matrix toolboxes. Step #0 done.
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9 % COMP(A) is often denoted by M(A) in the literature.
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11 % Reference (e.g.):
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12 % N.J. Higham, A survey of condition number estimation for
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13 % triangular matrices, SIAM Review, 29 (1987), pp. 575-596.
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15 if nargin == 1, k = 0; end
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16 [m, n] = size(A);
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17 p = min(m, n);
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19 if k == 0
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21 % This code uses less temporary storage than the `high level' definition above.
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22 C = -abs(A);
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23 for j=1:p
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24 C(j,j) = abs(A(j,j));
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25 end
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26
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27 elseif k == 1
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29 C = A';
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30 for j=1:p
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31 C(k,k) = 0;
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32 end
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33 mx = max(abs(C));
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34 C = -mx'*ones(1,n);
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35 for j=1:p
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36 C(j,j) = abs(A(j,j));
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37 end
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38 if all( A == tril(A) ), C = tril(C); end
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39 if all( A == triu(A) ), C = triu(C); end
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41 end