Add a useful package (from Source forge) for octave

[CreaPhase.git] / octave_packages / tsa-4.2.4 / histo4.m

diff --git a/octave_packages/tsa-4.2.4/histo4.m b/octave_packages/tsa-4.2.4/histo4.m
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+function [R, tix] = histo4(Y, W)
+% HISTO4 calculates histogram of multidimensional data samples 
+%   and supports data compression
+%
+% R = HISTO4(Y)
+% R = HISTO4(Y, W)
+%      Y    data: on sample per row, each sample has with size(Y,2) elements 
+%      W    weights of each sample (default: [])
+%           W = [] indicates that each sample has equal weight 
+%      R is a struct with these fields: 
+%       R.X  are the bin-values 
+%       R.H  is the frequency of occurence of value X (weighted with W)
+%      R.N  are the total number of samples (or sum of W)
+%
+% 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 8383 2011-07-16 20:06:59Z schloegl $
+%      Copyright (C) 1996-2005,2008,2009,2011 by Alois Schloegl <alois.schloegl@gmail.com>     
+%      This is part of the TSA-toolbox 
+%      http://pub.ist.ac.at/~schloegl/matlab/tsa/
+%
+%    This program is free software: you can redistribute it and/or modify
+%    it under the terms of the GNU General Public License as published by
+%    the Free Software Foundation, either version 3 of the License, or
+%    (at your option) any later version.
+%
+%    This program 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 General Public License for more details.
+%
+%    You should have received a copy of the GNU General Public License
+%    along with this program.  If not, see <http://www.gnu.org/licenses/>.
+
+
+%%%%% check input arguments %%%%%
+[yr, yc] = size(Y);
+if nargin<2, 
+       W = []; 
+end; 
+if ~isempty(W) && (yr ~= numel(W)),
+       error('number of rows of Y does not match number of elements in W');
+end; 
+
+%%%%% identify all possible X's and generate overall Histogram %%%%%
+[Y, idx] = sortrows(Y);
+
+d  = diff(Y,[],1);
+ix = any( (~isnan(d) & (d~=0) ) | diff(isnan(Y),[],1), 2);
+
+tmp = [find(ix); yr];
+R.X = Y(tmp,:);
+R.datatype = 'HISTOGRAM';
+if isempty(W)
+       R.H = [tmp(1); diff(tmp)];
+       R.N = yr;
+else
+       W   = cumsum(W(idx));
+       R.H = [W(tmp(1)); diff(W(tmp))];
+       R.N = W(end);
+end; 
+
+%%%%% generate inverse index %%%%%
+if nargout>1,
+        tix = cumsum([1;ix]);  % rank 
+        cc  = 1;
+        tmp = sum(ix);
+       if 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;
+       [tmp, idx] = sort(idx);        % inverse index
+        tix = tix(idx);                % inverse sort rank
+        
+        R.compressionratio = (prod(size(R.X)) + yr/cc) / (yr*yc);
+        R.tix = tix;
+end;
+