吴恩达机器学习作业7

pca

sigma = X' * X / m;
[U,S,V] = svd(sigma);

projectData

U_reduce = U(:,1:K);
Z = X * U_reduce;

recoverData

U_reduce = U(:,1:K);
X_rec = Z * U_reduce';

findClosestCentroids

m = size(X,1);
for i = 1:m
  ind_k = zeros(K,1);
  for j = 1:K
    ind_k(j) = sum((X(i,:) - centroids(j,:)) .^ 2);
  endfor
  [value,index] = min(ind_k);
  idx(i) = index;
endfor

computeCentroids

for i = 1:K
  centroids(i,:) = ((idx == i)' * X) / sum(idx == i);
endfor