49 lines
1.3 KiB
Matlab
Executable File
49 lines
1.3 KiB
Matlab
Executable File
function centroids = computeCentroids(X, idx, K)
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%COMPUTECENTROIDS returs the new centroids by computing the means of the
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%data points assigned to each centroid.
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% centroids = COMPUTECENTROIDS(X, idx, K) returns the new centroids by
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% computing the means of the data points assigned to each centroid. It is
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% given a dataset X where each row is a single data point, a vector
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% idx of centroid assignments (i.e. each entry in range [1..K]) for each
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% example, and K, the number of centroids. You should return a matrix
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% centroids, where each row of centroids is the mean of the data points
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% assigned to it.
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%
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% Useful variables
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[m n] = size(X);
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% You need to return the following variables correctly.
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centroids = zeros(K, n);
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% ====================== YOUR CODE HERE ======================
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% Instructions: Go over every centroid and compute mean of all points that
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% belong to it. Concretely, the row vector centroids(i, :)
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% should contain the mean of the data points assigned to
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% centroid i.
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%
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% Note: You can use a for-loop over the centroids to compute this.
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%
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freq = zeros(K, 1);
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for i=1:m,
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centroids(idx(i),:) += X(i,:);
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freq(idx(i)) += 1;
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end
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for i=1:n,
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centroids(:,i) ./= freq;
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end
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% =============================================================
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end
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