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40 lines
957 B
40 lines
957 B
#
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# Created: 20140207
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# Wirawan Purwanto
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#
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"""
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wpylib.array_tools
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Various tools for arrays (mainly, numpy array objects).
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"""
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def array_indices_cond_1d(arr, cond):
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"""Get the odered list of array indices whose corresponding elements satisfy
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a given condition.
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Useful for conditional assignment or evaluation.
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The input `cond' argument can be an ufunc-like function that evaluates
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a logical expression in bulk for each of the arr's element.
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Or it can be an array of logical values that has the same length as arr.
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Example use case:
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r = numpy.linspace(1.97, 3.5, num=150)
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i_select = cond_indices_1d(r, r <= 2.5)
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# ... then we can do something with r[i_select]
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# for conditional assignment or value extraction.
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"""
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arr = numpy.asarray(arr)
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assert len(arr.shape) == 1
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if callable(cond):
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cond = cond(arr)
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# otherwise, assume cond is already a good array
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return numpy.array(xrange(len(arr)))[ cond ]
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