project1.py 文件源码

def plotPrincipalComponents(principal1, principal2, X, y, classNames):
    C = len(classNames)    
    Y = X - np.ones((len(X),1))*X.mean(0)

    U,S,V = linalg.svd(Y,full_matrices=False)
    V = mat(V).T

    Z = Y * V

    # Plot PCA of the data
    f = figure()
    f.hold()
    title('Data projected onto Principal Components')
    for c in range(C):
        class_mask = y.A.ravel()==c
        plot(Z[class_mask,principal1], Z[class_mask,principal2], 'o')
    legend([convertToWord(i) for i in classNames])
    xlabel('PC{0}'.format(principal1+1))
    ylabel('PC{0}'.format(principal2+1))
    show()

# Gets the direction of a certain principal component