view minors.m @ 1198:2924b3a9b921 feature/d2_compatible

Add OpSet for fully compatible D2Variable, created from regular D2Variable by replacing d1 by first row of D1. Formal reduction by one order of accuracy at the boundary point.
author Martin Almquist <malmquist@stanford.edu>
date Fri, 16 Aug 2019 14:30:28 -0700
parents eaf557023fbe
children
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function [minor, sub] = minors(A, verbose)
    default_arg('verbose', true);
    [n, m] = size(A);

    if n ~= m
        error('A must be square');
    end

    sub = {};
    ks = {};

    ind = 1:n;
    for k = 1:n
        C = nchoosek(ind,k);
        for i = 1:size(C,1)
            ks{end + 1} = k;
            sub{end + 1} = A(C(i,:),C(i,:));
        end
    end

    for i = 1:length(sub)
        if verbose
            fprintf('%d:\n', ks{i});
            disp(sub{i})
        end

        minor(i) = det(sub{i});
    end
end


% A is positive semidefinite if all minors are non-negative
% A is negative semidefinite if all odd minors are non-positive and all even minors are non-negative