Statistics/Chi-squared distribution: Difference between revisions
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→{{header|Python}}: cdf function
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def χ2(x, k):
''' Chi-squared function, the probability distribution function (pdf) for chi-squared '''
return x
def gamma_cdf(k, x):
''' lower incomplete gamma by series formula with gamma '''
return x**k * exp(-x) * sum(x**m / gamma(k + m + 1) for m in range(100))
def cdf_χ2(x, k):
''' Cumulative probability function (cdf) for chi-squared '''
return gamma_cdf(k / 2, x / 2) if x
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