wehub-resource-sync
44 lines
972 B
Python
Executable File
44 lines
972 B
Python
Executable File
import numpy as np
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from prml.kernel.kernel import Kernel
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class PolynomialKernel(Kernel):
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"""
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Polynomial kernel
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k(x,y) = (x @ y + c)^M
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"""
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def __init__(self, degree=2, const=0.):
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"""
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construct Polynomial kernel
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Parameters
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----------
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const : float
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a constant to be added
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degree : int
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degree of polynomial order
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"""
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self.const = const
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self.degree = degree
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def __call__(self, x, y, pairwise=True):
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"""
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calculate pairwise polynomial kernel
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Parameters
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----------
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x : (..., ndim) ndarray
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input
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y : (..., ndim) ndarray
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another input with the same shape
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Returns
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-------
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output : ndarray
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polynomial kernel
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"""
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if pairwise:
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x, y = self._pairwise(x, y)
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return (np.sum(x * y, axis=-1) + self.const) ** self.degree
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