Why we use PCA just on 9-folder?

[xiaoxiongli]

Dear happynear,

@happynear

i find that you just use PCA on 9 folders(train_idx), and apply the pca result to 10 folders(train_idx+test_idx):

PCA: [U,mu,vars] = pca( [F1_mu(train_idx,:); F2_mu(train_idx,:)]' ); apply PCA: [F1PCA,F1PCAHat,~] = pcaApply( F1_mu', U, mu, dims );

so i wonder that why NOT use PCA on all of the folders other than just in 9 folders?

[happynear]

We should never see test examples in any way.