# scipy.special.fdtr¶

scipy.special.fdtr(dfn, dfd, x) = <ufunc 'fdtr'>

F cumulative distribution function.

Returns the value of the cumulative density function of the F-distribution, also known as Snedecor’s F-distribution or the Fisher-Snedecor distribution.

The F-distribution with parameters $$d_n$$ and $$d_d$$ is the distribution of the random variable,

$X = \frac{U_n/d_n}{U_d/d_d},$

where $$U_n$$ and $$U_d$$ are random variables distributed $$\chi^2$$, with $$d_n$$ and $$d_d$$ degrees of freedom, respectively.

Parameters: dfn : array_like First parameter (positive float). dfd : array_like Second parameter (positive float). x : array_like Argument (nonnegative float). y : ndarray The CDF of the F-distribution with parameters dfn and dfd at x.

Notes

The regularized incomplete beta function is used, according to the formula,

$F(d_n, d_d; x) = I_{xd_n/(d_d + xd_n)}(d_n/2, d_d/2).$

Wrapper for the Cephes [R409] routine fdtr.

References

 [R409] (1, 2) Cephes Mathematical Functions Library, http://www.netlib.org/cephes/index.html

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