computeCentriods.m

function centroids = computeCentroids(X, idx, K)

% Initialize to store new centroid values
centroids = zeros(K, n);

% iterate over number of centroids
for i = 1:K
  
    % create a boolean vector that match the current index, then use this to index into X
    has_this_centroid = X(idx == i, :);
  
    % sum up the examples that are assigned this centroid
    sum_of_assigned = sum(has_this_centroid);
  
    % get the number of assigned for easier averaging
    num_of_assigned = size(has_this_centroid, 1);
  
    % calulate and store new centroid
    centroids(i, :) = (1/num_of_assigned) * sum_of_assigned;
end 
  
end