Coverage for src/ensae_teaching_cs/ml/gini.py : 100%
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1"""
2@file
3@brief Functions about the `Gini coefficient <https://en.wikipedia.org/wiki/Gini_coefficient>`_.
4"""
5import numpy
8def gini(Y, X=None):
9 """
10 Computes the
11 `Gini coefficients <https://en.wikipedia.org/wiki/Gini_coefficient>`_.
13 @param Y Y values (or revenues)
14 @param X None for a uniform population or not None for already order value.
15 @return a curve ``(x, Gini(x))``
16 """
17 n = len(Y)
18 couples = numpy.empty((n, 2))
19 if X is None:
20 couples[:, 0] = 1
21 else:
22 couples[:, 0] = X
23 couples[:, 1] = Y
24 couples = numpy.cumsum(couples, axis=0)
25 couples[:, 0] /= max(couples[n - 1, 0], 1e-7)
26 couples[:, 1] /= max(couples[n - 1, 1], 1e-7)
28 g = 0.
29 n = couples.shape[0]
31 for i in range(0, n):
32 dx = couples[i, 0] - couples[i - 1, 0]
33 y = couples[i - 1, 1] + couples[i, 1]
34 g += dx * y
36 return (1. - g) / 2