spm_perm_mtx.m
8a186cd82567master

spm_perm_mtx.m
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			function [K] = spm_perm_mtx(n)
			% Returns a matrix of indices permuted over n
			% FORMAT [K] = spm_perm_mtx(n)
			% n - (scalar) number of indices
			% K - (2^n x n) permutation matrix
			% n - (vector) indices
			% K - (length(n)! x n) permutation matrix
			%__________________________________________________________________________
			% Copyright (C) 2008 Wellcome Trust Centre for Neuroimaging

			% Karl Friston
			% $Id: spm_perm_mtx.m 5657 2013-09-26 16:53:40Z karl $

			% get permutations
			%==========================================================================

			% permute zeros and ones
			%--------------------------------------------------------------------------
			if isscalar(n)

			N = 2^n;
			K = sparse(N,n);
			x = sparse(1,1,1,2,1);
			for i = 1:n
			y = ones(N/length(x),1);
			K(:,i) = kron(x,y);
			x = [x;x];
			end

			% permute indices
			%--------------------------------------------------------------------------
			elseif isvector(n)

			n = n(:);
			K = n;
			while size(K,2) < length(n)
			x = [];
			for i = 1:size(K,1)
			d = K(i,:);
			r = n;
			for j = 1:length(d)
			r(r == d(j)) = [];
			end
			x = [x; [kron(ones(length(r),1),d) r]];
			end
			K = x;
			end
			end

			% make logical
			%--------------------------------------------------------------------------
			K = logical(K);