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Prepare private _rank() function to be made public. (#96372)
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@ -355,7 +355,8 @@ def _fail_neg(values, errmsg='negative value'):
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raise StatisticsError(errmsg)
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yield x
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def _rank(data, /, *, key=None, reverse=False, ties='average') -> list[float]:
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def _rank(data, /, *, key=None, reverse=False, ties='average', start=1) -> list[float]:
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"""Rank order a dataset. The lowest value has rank 1.
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Ties are averaged so that equal values receive the same rank:
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@ -369,14 +370,22 @@ def _rank(data, /, *, key=None, reverse=False, ties='average') -> list[float]:
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>>> _rank([3.5, 5.0, 3.5, 2.0, 6.0, 1.0])
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[3.5, 5.0, 3.5, 2.0, 6.0, 1.0]
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It is possible to rank the data in reverse order so that
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the highest value has rank 1. Also, a key-function can
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extract the field to be ranked:
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It is possible to rank the data in reverse order so that the
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highest value has rank 1. Also, a key-function can extract
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the field to be ranked:
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>>> goals = [('eagles', 45), ('bears', 48), ('lions', 44)]
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>>> _rank(goals, key=itemgetter(1), reverse=True)
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[2.0, 1.0, 3.0]
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Ranks are conventionally numbered starting from one; however,
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setting *start* to zero allow the ranks to be used as array indices:
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>>> prize = ['Gold', 'Silver', 'Bronze', 'Certificate']
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>>> scores = [8.1, 7.3, 9.4, 8.3]
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>>> [prize[int(i)] for i in _rank(scores, start=0, reverse=True)]
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['Bronze', 'Certificate', 'Gold', 'Silver']
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"""
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# If this function becomes public at some point, more thought
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# needs to be given to the signature. A list of ints is
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@ -389,7 +398,7 @@ def _rank(data, /, *, key=None, reverse=False, ties='average') -> list[float]:
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if key is not None:
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data = map(key, data)
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val_pos = sorted(zip(data, count()), reverse=reverse)
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i = 0 # To rank starting at 0 instead of 1, set i = -1.
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i = start - 1
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result = [0] * len(val_pos)
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for _, g in groupby(val_pos, key=itemgetter(0)):
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group = list(g)
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@ -400,6 +409,7 @@ def _rank(data, /, *, key=None, reverse=False, ties='average') -> list[float]:
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i += size
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return result
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def _integer_sqrt_of_frac_rto(n: int, m: int) -> int:
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"""Square root of n/m, rounded to the nearest integer using round-to-odd."""
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# Reference: https://www.lri.fr/~melquion/doc/05-imacs17_1-expose.pdf
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