[Octave-cvsupdate] SF.net SVN: octave:[9456] trunk/octave-forge/main/statistics

[<as...@us...>]

Revision: 9456
          http://octave.svn.sourceforge.net/octave/?rev=9456&view=rev
Author:   asnelt
Date:     2011-12-22 13:22:04 +0000 (Thu, 22 Dec 2011)
Log Message:
-----------
Initial commit.

Modified Paths:
--------------
    trunk/octave-forge/main/statistics/INDEX
    trunk/octave-forge/main/statistics/NEWS

Added Paths:
-----------
    trunk/octave-forge/main/statistics/inst/kmeans.m

Modified: trunk/octave-forge/main/statistics/INDEX
===================================================================
--- trunk/octave-forge/main/statistics/INDEX	2011-12-21 21:33:00 UTC (rev 9455)
+++ trunk/octave-forge/main/statistics/INDEX	2011-12-22 13:22:04 UTC (rev 9456)
@@ -62,8 +62,9 @@
 Fitting
  gamfit
 Clustering
+ kmeans
+ linkage
  pdist
- linkage
  squareform
 Reading and Writing
  caseread

Modified: trunk/octave-forge/main/statistics/NEWS
===================================================================
--- trunk/octave-forge/main/statistics/NEWS	2011-12-21 21:33:00 UTC (rev 9455)
+++ trunk/octave-forge/main/statistics/NEWS	2011-12-22 13:22:04 UTC (rev 9456)
@@ -1,9 +1,9 @@
 Summary of important user-visible changes for statistics 1XXXXXXXX:
 -------------------------------------------------------------------
 
- ** The following functions are new in 1.1.0:
+ ** The following functions are new in 1.1.X:
 
-      monotone_smooth
+      monotone_smooth kmeans
 
  ** Bug fixes on the function:
 

Added: trunk/octave-forge/main/statistics/inst/kmeans.m
===================================================================
--- trunk/octave-forge/main/statistics/inst/kmeans.m	                        (rev 0)
+++ trunk/octave-forge/main/statistics/inst/kmeans.m	2011-12-22 13:22:04 UTC (rev 9456)
@@ -0,0 +1,84 @@
+## Copyright (C) 2011 Soren Hauberg
+## 
+## 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, write to the Free Software
+## Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+function [classes, centers] = kmeans (data, k, varargin)
+  ## Input checking
+  if (!ismatrix (data) || !isreal (data))
+    error ("kmeans: first input argument must be a DxN real data matrix");
+  endif
+  if (!isscalar (k))
+    error ("kmeans: second input argument must be a scalar");
+  endif
+  
+  [N, D] = size (data);
+  
+  ## (so far) Harcoded options
+  maxiter = Inf;
+  start = "sample";
+  
+  ## Find initial clusters
+  switch (lower (start))
+    case "sample"
+      idx = randperm (N) (1:k);
+      centers = data (idx, :);
+    otherwise
+      error ("kmeans: unsupported initial clustering parameter");
+  endswitch
+  
+  ## Run the algorithm
+  D = zeros (N, k);
+  iterations = 0;
+  prevcenters = centers;
+  while (true)
+    ## Compute distances
+    for i = 1:k
+      D (:, i) = sum (( data - repmat (centers (i, :), N, 1)).^2, 2);
+    endfor
+    
+    ## Classify
+    [tmp, classes] = min (D, [], 2);
+    
+    ## Recompute centers
+    for i = 1:k
+      centers (i, :) = mean (data (classes == i, :));
+    endfor
+    
+    ## Check for convergence
+    iterations++;
+    if (all (centers (:) == prevcenters (:)) || iterations >= maxiter)
+      break;
+    endif
+    prevcenters = centers;
+  endwhile
+endfunction
+
+%!demo
+%! ## Generate a two-cluster problem
+%! C1 = randn (100, 2) + 1;
+%! C2 = randn (100, 2) - 1;
+%! data = [C1; C2];
+%!
+%! ## Perform clustering
+%! [idx, centers] = kmeans (data, 2);
+%!
+%! ## Plot the result
+%! figure
+%! plot (data (idx==1, 1), data (idx==1, 2), 'ro');
+%! hold on
+%! plot (data (idx==2, 1), data (idx==2, 2), 'bs');
+%! plot (centers (:, 1), centers (:, 2), 'kv', 'markersize', 10);
+%! hold off
+

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