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lines changed Original file line number Diff line number Diff line change 139
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from operator import itemgetter , mul
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from collections import Counter , namedtuple
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+ _SQRT2 = sqrt (2.0 )
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+
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# === Exceptions ===
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class StatisticsError (ValueError ):
@@ -1102,7 +1104,7 @@ def cdf(self, x):
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"Cumulative distribution function. P(X <= x)"
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if not self ._sigma :
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raise StatisticsError ('cdf() not defined when sigma is zero' )
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- return 0.5 * (1.0 + erf ((x - self ._mu ) / (self ._sigma * sqrt ( 2.0 ) )))
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+ return 0.5 * (1.0 + erf ((x - self ._mu ) / (self ._sigma * _SQRT2 )))
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def inv_cdf (self , p ):
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"""Inverse cumulative distribution function. x : P(X <= x) = p
@@ -1158,7 +1160,7 @@ def overlap(self, other):
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dv = Y_var - X_var
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dm = fabs (Y ._mu - X ._mu )
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if not dv :
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- return 1.0 - erf (dm / (2.0 * X ._sigma * sqrt ( 2.0 ) ))
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+ return 1.0 - erf (dm / (2.0 * X ._sigma * _SQRT2 ))
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a = X ._mu * Y_var - Y ._mu * X_var
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b = X ._sigma * Y ._sigma * sqrt (dm * dm + dv * log (Y_var / X_var ))
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x1 = (a + b ) / dv
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