% RANDOMSAMPLE - selects n random items from an array%% Usage:  items = randomsample(a, n)%% Arguments:    a - Either an array of values from which the items are to%                   be selected, or an integer in which case the items%                   are values selected from the array [1:a]%               n - The number of items to be selected.%%% This function can be used as a basic replacement for RANDSAMPLE for those% who do not have the statistics toolbox.% Also,%    r = randomsample(n,n) will give a random permutation of the integers 1:n %% See also: RANSAC% Strategy is to generate a random integer index into the array and select that% item from the array.  The selected element in the array is then overwritten by% the last element in the array and the process is then repeated except that% when we select the next element we generate a random integer index that lies% in the range 1 to arraylength - 1, and so on.  This ensures items are not% repeated.% Copyright (c) 2006 Peter Kovesi% School of Computer Science & Software Engineering% The University of Western Australia% pk at csse uwa edu au    % http://www.csse.uwa.edu.au/~pk% % Permission is hereby granted, free of charge, to any person obtaining a copy% of this software and associated documentation files (the "Software"), to deal% in the Software without restriction, subject to the following conditions:% % The above copyright notice and this permission notice shall be included in % all copies or substantial portions of the Software.%% The Software is provided "as is", without warranty of any kind.% September   2006 function item = randomsample(a, n)        npts = length(a);    if npts == 1   % We have a scalar argument for a	npts = a;	a = [1:a]; % Construct an array 1:a    end        if npts < n	error(...	sprintf('Trying to select %d items from a list of length %d',n, npts));    end        item = zeros(1,n);        for i = 1:n	% Generate random value in the appropriate range 	r = ceil((npts-i+1).*rand);	item(i) = a(r);       % Select the rth element from the list	a(r)    = a(end-i+1); % Overwrite selected element    end                       % ... and repeat