Cursera: machine learning ex7.

machine_learning/mlclass-ex7-008/mlclass-ex7/runkMeans.m

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+function [centroids, idx] = runkMeans(X, initial_centroids, ...
+                                      max_iters, plot_progress)
+%RUNKMEANS runs the K-Means algorithm on data matrix X, where each row of X
+%is a single example
+%   [centroids, idx] = RUNKMEANS(X, initial_centroids, max_iters, ...
+%   plot_progress) runs the K-Means algorithm on data matrix X, where each 
+%   row of X is a single example. It uses initial_centroids used as the
+%   initial centroids. max_iters specifies the total number of interactions 
+%   of K-Means to execute. plot_progress is a true/false flag that 
+%   indicates if the function should also plot its progress as the 
+%   learning happens. This is set to false by default. runkMeans returns 
+%   centroids, a Kxn matrix of the computed centroids and idx, a m x 1 
+%   vector of centroid assignments (i.e. each entry in range [1..K])
+%
+
+% Set default value for plot progress
+if ~exist('plot_progress', 'var') || isempty(plot_progress)
+    plot_progress = false;
+end
+
+% Plot the data if we are plotting progress
+if plot_progress
+    figure;
+    hold on;
+end
+
+% Initialize values
+[m n] = size(X);
+K = size(initial_centroids, 1);
+centroids = initial_centroids;
+previous_centroids = centroids;
+idx = zeros(m, 1);
+
+% Run K-Means
+for i=1:max_iters
+    
+    % Output progress
+    fprintf('K-Means iteration %d/%d...\n', i, max_iters);
+    if exist('OCTAVE_VERSION')
+        fflush(stdout);
+    end
+    
+    % For each example in X, assign it to the closest centroid
+    idx = findClosestCentroids(X, centroids);
+    
+    % Optionally, plot progress here
+    if plot_progress
+        plotProgresskMeans(X, centroids, previous_centroids, idx, K, i);
+        previous_centroids = centroids;
+        fprintf('Press enter to continue.\n');
+        pause;
+    end
+    
+    % Given the memberships, compute new centroids
+    centroids = computeCentroids(X, idx, K);
+end
+
+% Hold off if we are plotting progress
+if plot_progress
+    hold off;
+end
+
+end
+