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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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8f23314345f4 Create local repository for matrix toolboxes. Step #0 done.
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1 function see(A, k)
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2 %SEE Pictures of a matrix.
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3 % SEE(A) displays MESH(A), SEMILOGY(SVD(A),'o'),
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4 % and (if A is square) PS(A) and FV(A) in four subplot windows.
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5 % SEE(A, 1) plots MESH(PINV(A)) in the
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6 % third window instead of the 1e-3-pseudospectrum.
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7 % SEE(A, -1) plots only the eigenvalues in the third/fourth window,
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8 % which is much quicker than PS or FV.
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9 % If A is complex, only real parts are used for the mesh plots.
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10 % If A is sparse, just SPY(A) is shown.
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11
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12 if nargin < 2, k = 0; end
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13 [m, n] = size(A);
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14 square = (m == n);
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15 clf
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16
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17 if issparse(A)
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18
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19 spy(A);
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20
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21 else
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22
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23 B = pinv(A);
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24 s = svd(A);
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25 zs = (s == zeros(size(s)));
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26 if any( zs )
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27 s( zs ) = []; % Remove zero singular values for semilogy plot.
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28 end
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29
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30 subplot(2,2,1)
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31 mesh(real(A)), axis('ij'), drawnow
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32 subplot(2,2,2)
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33 semilogy(s, 'o')
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34 hold on, semilogy(s, '-'), hold off, drawnow
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35 if any(zs), title('Zero(s) omitted'), end
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36
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37 subplot(2,2,3)
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38 if ~square
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39 axis off
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40 text(0,0,'Matrix not square.')
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41 return
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42 end
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43
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44 if k == -1
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45 ps(A, 0);
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46 elseif k == 1
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47 mesh(real(B)), axis('ij'), drawnow
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48 else
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49 ps(A);
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50 end
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51
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52 subplot(2,2,4)
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53 fv(A);
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54
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55 end