45 lines
865 B
Python
45 lines
865 B
Python
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def find_maxima(x):
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"""Find local maxima of x.
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Example:
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>>> x = [1, 3, -2, 0, 2, 1]
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>>> find_maxima(x)
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[1, 4]
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If in a local maximum several elements have the same value,
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return the left-most index.
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Example:
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>>> x = [1, 2, 2, 1]
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>>> find_maxima(x)
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[1]
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Input arguments:
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x -- 1D list of real numbers
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Output:
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idx -- list of indices of the local maxima in x
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"""
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idx = []
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up = False
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down = False
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for i in range(len(x)):
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if i == 0 or x[i-1] < x[i]:
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up = True
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up_idx = i
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elif x[i-1] > x[i]:
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up = False
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# if x[i-1] == x[i], no change
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if i+1 == len(x) or x[i+1] < x[i]:
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down = True
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elif x[i+1] > x[i]:
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down = False
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if up and down:
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idx.append(up_idx)
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return idx
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