function [Y,I] = randmat(X,DIM)
%RANDMAT Shuffles array elements or cell elements randomly.
% For vectors, RANDMAT(X) shuffles the array by calling randperm - use
% randperm instead.
% For matrices, RANDMAT(X) shuffles the elements randomly.
% RANDMAT works for 1 or 2 dimensions.
%
% Y = RANDMAT(X,DIM)
% has an optional parameter.
% DIM selects a dimension to shuffle randomly.
% The result is in Y which has same shape and type as X.
%
% [Y,I] = RANDMAT(X,DIM) also returns an index matrix I.
% If X is a vector, then Y = X(I).
% If X is an m-by-n matrix and DIM=1, then
% for j = 1:n, Y(:,j) = X(I(:,j),j); end
%
%
% Example: if X = [1 2 3
% 4 5 6]
%
% then RANDMAT(X,1) might be [1 5 3 and RANDMAT(X,2) might be [3 2 1
% 4 2 6] 4 6 5]
%
% See also PERMS, RAND.
% Author: Peter Bodin <pbodin@kth.se>
%
% 2005-11-20 Peter Bodin <pbodin@kth.se>
% * Second revision
%
% Removed the setting of the rand seed so that this function wont
% disturb peoples manually set seeds. Thanks to John D'Errico who
% explained why this should not be done.
msg = nargchk(1, 2, nargin); % check input
error(msg);
if ndims(X)>2
error('RANDMAT works for 1 or 2 dimensions only.')
end
[r,c] = size(X); % size
switch nargin % argument switch
case 1 || isvector(X)
I = reshape(randperm(numel(X)),[r c]); % use randperm if vector
Y = X(I); % or if all elements should be shuffled
case 2
switch DIM % dimension switch
case 1
[I,I] = sort(rand([r c]),1); % random row permutations
Y = X(I+ repmat([0 (r+1:r:c*r)-1],r,1));
case 2
[Y,I] = randmat(X',1); % use transposed input for columns
Y = Y';
otherwise
error('RANDMAT works for 1 or 2 dimensions only.')
end
end
