Andrew Ng机器学习week8(Unsupervised Learning)编程习题

findClosestCentroids.m

function idx = findClosestCentroids(X, centroids) %FINDCLOSESTCENTROIDS computes the centroid memberships for every example % idx = FINDCLOSESTCENTROIDS (X, centroids) returns the closest centroids % in idx for a dataset X where each row is a single example. idx = m x 1 % vector of centroid assignments (i.e. each entry in range [1..K]) % % Set K K = size(centroids, 1); % You need to return the following variables correctly. idx = zeros(size(X,1), 1); % ====================== YOUR CODE HERE ====================== % Instructions: Go over every example, find its closest centroid, and store % the index inside idx at the appropriate location. % Concretely, idx(i) should contain the index of the centroid % closest to example i. Hence, it should be a value in the % range 1..K % % Note: You can use a for-loop over the examples to compute this. % for i=1:size(X, 1) for j=1:K distance(j) = norm(X(i,:)-centroids(j,:))^2; end [minr, index] = min(distance); idx(i)=index; end % ============================================================= end

computeCentroids.m

function centroids = computeCentroids(X, idx, K) %COMPUTECENTROIDS returns the new centroids by computing the means of the