function [R,tix]=histo4(Y) % HISTO4 calculates histogram for rows and supports data compression % % R = HISTO4(Y) % R is a struct with th fields % R.X are the bin-values % R.H is the frequency of occurence of value X % R.N are the number of samples % % HISTO4 might be useful for data compression, because % [R,tix] = histo4(Y) % is the compression step % R.X(tix,:) % is the decompression step % % The effort (in memory and speed) for compression is O(n*log(n)) % The effort (in memory and speed) for decompression is only O(n) % % see also: HISTO, HISTO2, HISTO3, HISTO4 % % REFERENCE(S): % C.E. Shannon and W. Weaver "The mathematical theory of communication" University of Illinois Press, Urbana 1949 (reprint 1963). % $Id: histo4.m 4585 2008-02-04 13:47:45Z adb014 $ % Copyright (C) 1996-2005 by Alois Schloegl <a.schloegl@ieee.org> % This is part of the TSA-toolbox % http://www.dpmi.tugraz.at/~schloegl/matlab/tsa/ % This library is free software; you can redistribute it and/or % modify it under the terms of the GNU Library General Public % License as published by the Free Software Foundation; either % Version 2 of the License, or (at your option) any later version. % % This library is distributed in the hope that it will be useful, % but WITHOUT ANY WARRANTY; without even the implied warranty of % MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU % Library General Public License for more details. % % You should have received a copy of the GNU Library General Public % License along with this library; If not, see <http://www.gnu.org/licenses/>. [yr, yc] = size(Y); if yr==1, % Makes sure there is a second row % Sort does not support the DIM-argument, therefore, % this function would not work correctly with this software % Once this is fixed, this part can be removed. Y = [Y; NaN+ones(size(Y))]; end; % identify all possible X's and overall Histogram [Y, idx] = sortrows(Y); [tmp, idx] = sort(idx); % inverse index %[ix, iy] = (diff(Y,1)>0); ix = logical(zeros(yr-1,1)); for k = 1:yr-1, ix(k) = any(Y(k,:)~=Y(k+1,:)); end; tmp = [find(ix); yr]; R.H = diff([0; tmp]); R.X = Y(tmp,:); R.N = yr; R.datatype = 'HISTOGRAM'; % generate inverse index if nargout>1, tix = cumsum([1;ix]); % rank cc = 1; tmp = sum(ix)+1; if 0, exist('OCTAVE_VERSION','builtin'), ; % NOP; no support for integer datatyp elseif tmp <= 2^8; tix = uint8(tix); cc = 8/1; elseif tmp <= 2^16; tix = uint16(tix); cc = 8/2; elseif tmp <= 2^32; tix = uint32(tix); cc = 8/4; end; tix = tix(idx); % inverse sort rank R.compressionratio = (prod(size(R.X)) + yr/cc) / (yr*yc); R.tix = tix; end;

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