33 lines
814 B
Python
33 lines
814 B
Python
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"""
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pca_limitations
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~~~~~~~~~~~~~~~
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Plot graphs to illustrate the limitations of PCA.
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"""
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# Third-party libraries
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from mpl_toolkits.mplot3d import Axes3D
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import matplotlib.pyplot as plt
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import numpy as np
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# Plot just the data
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fig = plt.figure()
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ax = fig.gca(projection='3d')
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z = np.linspace(-2, 2, 20)
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theta = np.linspace(-4 * np.pi, 4 * np.pi, 20)
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x = np.sin(theta)+0.03*np.random.randn(20)
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y = np.cos(theta)+0.03*np.random.randn(20)
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ax.plot(x, y, z, 'ro')
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plt.show()
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# Plot the data and the helix together
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fig = plt.figure()
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ax = fig.gca(projection='3d')
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z_helix = np.linspace(-2, 2, 100)
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theta_helix = np.linspace(-4 * np.pi, 4 * np.pi, 100)
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x_helix = np.sin(theta_helix)
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y_helix = np.cos(theta_helix)
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ax.plot(x, y, z, 'ro')
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ax.plot(x_helix, y_helix, z_helix, '')
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plt.show()
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