Statistics/Chi-squared distribution: Difference between revisions
Content added Content deleted
(→{{header|Julia}}: gamma) |
m (→{{header|Python}}: cdf function) |
||
| Line 308: | Line 308: | ||
def χ2(x, k): |
def χ2(x, k): |
||
''' Chi-squared function, the probability distribution function (pdf) for chi-squared ''' |
''' Chi-squared function, the probability distribution function (pdf) for chi-squared ''' |
||
return x |
return x**(k/2 - 1) * exp(-x/2) / (2**(k/2) * gamma(k / 2)) if x > 0 and k > 0 else 0.0 |
||
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): |
def cdf_χ2(x, k): |
||
''' Cumulative probability function (cdf) for chi-squared ''' |
''' Cumulative probability function (cdf) for chi-squared ''' |
||
if x |
return gamma_cdf(k / 2, x / 2) if x > 0 and k > 0 else 0.0 |
||
return 0 |
|||
return gammainc(k / 2, x / 2) |
|||