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import numpy as np |
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def delta(feat, window): |
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assert window > 0 |
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delta_feat = np.zeros_like(feat) |
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for i in range(1, window + 1): |
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delta_feat[:-i] += i * feat[i:] |
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delta_feat[i:] += -i * feat[:-i] |
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delta_feat[-i:] += i * feat[-1] |
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delta_feat[:i] += -i * feat[0] |
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delta_feat /= 2 * sum(i ** 2 for i in range(1, window + 1)) |
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return delta_feat |
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def add_deltas(x, window=2, order=2): |
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feats = [x] |
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for _ in range(order): |
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feats.append(delta(feats[-1], window)) |
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return np.concatenate(feats, axis=1) |
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class AddDeltas(object): |
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def __init__(self, window=2, order=2): |
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self.window = window |
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self.order = order |
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def __repr__(self): |
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return "{name}(window={window}, order={order}".format( |
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name=self.__class__.__name__, window=self.window, order=self.order |
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) |
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def __call__(self, x): |
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return add_deltas(x, window=self.window, order=self.order) |
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