44 lines
1.2 KiB
Python
44 lines
1.2 KiB
Python
"""
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misleading_gradient
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~~~~~~~~~~~~~~~~~~~
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Plots a function which misleads the gradient descent algorithm."""
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#### Libraries
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# Third party libraries
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from matplotlib.ticker import LinearLocator
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# Note that axes3d is not explicitly used in the code, but is needed
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# to register the 3d plot type correctly
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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
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fig = plt.figure()
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ax = fig.gca(projection='3d')
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X = numpy.arange(-1, 1, 0.025)
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Y = numpy.arange(-1, 1, 0.025)
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X, Y = numpy.meshgrid(X, Y)
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Z = X**2 + 10*Y**2
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colortuple = ('w', 'b')
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colors = numpy.empty(X.shape, dtype=str)
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for x in xrange(len(X)):
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for y in xrange(len(Y)):
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colors[x, y] = colortuple[(x + y) % 2]
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surf = ax.plot_surface(X, Y, Z, rstride=1, cstride=1, facecolors=colors,
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linewidth=0)
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ax.set_xlim3d(-1, 1)
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ax.set_ylim3d(-1, 1)
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ax.set_zlim3d(0, 12)
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ax.w_xaxis.set_major_locator(LinearLocator(3))
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ax.w_yaxis.set_major_locator(LinearLocator(3))
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ax.w_zaxis.set_major_locator(LinearLocator(3))
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ax.text(0.05, -1.8, 0, "$w_1$", fontsize=20)
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ax.text(1.5, -0.25, 0, "$w_2$", fontsize=20)
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ax.text(1.79, 0, 9.62, "$C$", fontsize=20)
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plt.show()
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