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annotate minors.m @ 577:e45c9b56d50d feature/grids

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Add an Empty grid class The need turned up for the flexural code when we may or may not have a grid for the open water and want to plot that solution. In case there is no open water we need an empty grid to plot the empty gridfunction against to avoid errors.
author Jonatan Werpers <jonatan@werpers.com>
date Thu, 07 Sep 2017 09:16:12 +0200
parents eaf557023fbe
children
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eaf557023fbe Added verbose flag to semiDefIneq and minors.
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1 function [minor, sub] = minors(A, verbose)
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2 default_arg('verbose', true);
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3 [n, m] = size(A);
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5 if n ~= m
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6 error('A must be square');
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7 end
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9 sub = {};
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10 ks = {};
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11
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12 ind = 1:n;
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13 for k = 1:n
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14 C = nchoosek(ind,k);
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15 for i = 1:size(C,1)
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16 ks{end + 1} = k;
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17 sub{end + 1} = A(C(i,:),C(i,:));
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18 end
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19 end
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21 for i = 1:length(sub)
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22 if verbose
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23 fprintf('%d:\n', ks{i});
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24 disp(sub{i})
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25 end
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27 minor(i) = det(sub{i});
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28 end
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29 end
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32 % A is positive semidefinite if all minors are non-negative
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33 % A is negative semidefinite if all odd minors are non-positive and all even minors are non-negative
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