function [out]=randomizeAO(m, n)
% function [out]=randomize(in, n)
% By Angel Otarola
% aotarola@email.arizona.edu
%
% description: This routine generates a vector which includes 'n' unique
% randomly generated indexes.

% inputs are:
%          m = number of elements in the vector to be randomized.
%          n = number of elements to be included in the randomized output array
%
% output:
%          out=a vector which contains the indexes of the randomized vector

%
% Example:
%       ---If the original array has 660 elements and we want to generate a
%       sequence of 100 elements randomly picked from the total of 660
%       possible indexes, we do the following:
%
%       out=randomizeAO(660,100);
%
%
%       A more simple example is the following:
%       
%       out=randomizeAO(15,15);
%
%       The ouput might give something like the following:
%       5,9,1,12,15,3,7,11,10,13,6,14,4,8,2
%       As noticed the order of the elements has been randomized and they
%       are all unique.


x=[1:1:m];    %%% position indexes of the original vector of length m;

%%% initilizes the state of the random number generators each time this
%%% routine is called. This guarantees numbers out of a unique sequence of
%%% every time.

rand('twister',sum(100*clock));

%%% The following code produces 'n' random unique ocurrences indexes

for i=1:n,           %% produces 'n' random indexes
    not_done=1;      %% operational flag

    if i==1,         
        out(i)=floor(rand(1)*m)+1;  %% this is the first index obtained in a random way
    else
        while not_done,             %% this is to make sure the next random index is
                                    %% different than the ones already
                                    %% generated.
            rindex = floor(rand(1)*m)+1;     %% produces a random index
            indexes=find(out == rindex);     %% check if rindex is already in the ones generated
            if length(indexes) == 0,         %% this is true if rindex is unique and has not been previously generated
               out(i) = rindex;              %% stores the unique index generated in the output array
               not_done = 0;                 %% we are done
            end
        end
    end
end
        
out=out(:);      %% makes sure the output array is a column vector