%F=frequency(x) is the vector whose components are the
%frequencies with which each symbol in x appears in x,
%from most frequent to least frequent.
%x is assumed to be a data vector with integer components.
%
% Usage:
%	F =  frequency( [ 11 11 11 11 22 22 -3 -3 4 5 11 ] )'
% returns F = [ 5     2     2     1     1 ],
% meaning that
% the most frequent symbol ("11") appears 5 times,
% the second most frequent symbol ("22")
% occurs 2 times, etc.
% See HUFFMANLENGTH, SORTED_KRAFT, ENTROPY, HISTO.

% documented in
%   ftp://oz.ee.umn.edu/users/kieffer/seminar/notes3.pdf
% Change log:
% 1999-06-29:DAV: factored "frequency" into 2 routines,
%   "frequency" and "histo".
% 1999-06-24:DAV: David Cary <d.cary at ieee.org> added documentation
% ???:JCK: John C. Kieffer wrote original version and put online at
%   http://www.ee.umn.edu/users/kieffer/programs.html

function F = frequency(x)
minimum = min(x(:)); 
if( minimum < 0 ) 
   h = histo(x(:)-minimum); 
else
   h = histo(x(:));
end;
% eliminate zeros
h = h( find(h) );
% sort by most-frequent-first.
F = flipUD( sort(h) );

% end frequency.m.