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import matplotlib.pyplot as plt | |
import numpy as np | |
from numpy import array | |
from sklearn.decomposition import PCA | |
D = array([[1, 1],[2, 2],[3, 3],[4, 4],[5, 5], # Matrix D has all the | |
[6, 6],[7, 7],[8, 8],[9, 9]]) # points on line x = y | |
# Adding noise: | |
E = np.zeros(np.shape(D)) | |
E = D + np.random.rand(np.shape(D)[0], np.shape(D)[1]) | |
from sklearn.preprocessing import MinMaxScaler | |
E = MinMaxScaler().fit_transform(E) | |
D = MinMaxScaler().fit_transform(D.astype(float)) | |
# create the transform | |
pca = PCA(1) | |
# fit transform | |
pca.fit(E) | |
# access values and vectors | |
print('EigenVector(PCA component): ', pca.components_) | |
print('Explained variance: ', pca.explained_variance_) | |
F = pca.transform(E) | |
E_projected = pca.inverse_transform(F) | |
plt.figure(figsize=(15,5)) | |
plt.subplot(1,2,1) | |
plt.scatter(D[:,0], D[:,1], color= 'lime', label = 'true data') | |
plt.scatter(E[:,0], E[:,1], color= 'black', label= 'after noise addition') | |
plt.xticks(np.arange(0, 1.1, .1)) | |
plt.yticks(np.arange(0, 1.1, .1)) | |
plt.legend() | |
plt.subplot(1,2,2) | |
plt.scatter(D[:,0], D[:,1], color= 'lime', label = 'true data') | |
plt.scatter(E_projected[:, 0], E_projected[:, 1], | |
color = 'red', label= 'PCA projection of noisy data') | |
pca.components_[0] = pca.components_[0] / min(pca.components_[0]) | |
plt.quiver(*([0,0]), pca.components_[0][0], pca.components_[0][1], | |
angles='xy', scale_units='xy', scale=1, color='pink', | |
alpha = 0.6, label= 'Principle Component(Rescaled Eigenvector)') | |
plt.xticks(np.arange(0, 1.1, .1)) | |
plt.yticks(np.arange(0, 1.1, .1)) | |
plt.legend() | |
plt.show() | |
Output: | |
EigenVector(PCA component): [[0.73552669 0.67749575]] | |
Explained variance: [0.22817895] |
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