Mercurial > repos > public > sbplib
comparison minors.m @ 167:15baeb35f74e feature/grids
Merge in changes from default.
| author | Jonatan Werpers <jonatan@werpers.com> |
|---|---|
| date | Tue, 23 Feb 2016 13:25:43 +0100 |
| parents | 0a881a3dc9a9 |
| children | eaf557023fbe |
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| 166:7cb97c1988d9 | 167:15baeb35f74e |
|---|---|
| 1 function [minor, sub] = minors(A) | |
| 2 [n, m] = size(A); | |
| 3 | |
| 4 if n ~= m | |
| 5 error('A must be square'); | |
| 6 end | |
| 7 | |
| 8 sub = {}; | |
| 9 ks = {}; | |
| 10 | |
| 11 ind = 1:n; | |
| 12 for k = 1:n | |
| 13 C = nchoosek(ind,k); | |
| 14 for i = 1:size(C,1) | |
| 15 ks{end + 1} = k; | |
| 16 sub{end + 1} = A(C(i,:),C(i,:)); | |
| 17 end | |
| 18 end | |
| 19 | |
| 20 for i = 1:length(sub) | |
| 21 fprintf('%d:\n', ks{i}); | |
| 22 disp(sub{i}) | |
| 23 | |
| 24 minor(i) = det(sub{i}); | |
| 25 end | |
| 26 end | |
| 27 | |
| 28 | |
| 29 % A is positive semidefinite if all minors are non-negative | |
| 30 % A is negative semidefinite if all odd minors are non-positive and all even minors are non-negative | |
| 31 |