scipy.special.btdtria#

scipy.special.btdtria(p, b, x, out=None) = <ufunc 'btdtria'>#

Inverse of betainc with respect to a.

This is the inverse of the beta cumulative distribution function, betainc, considered as a function of a, returning the value of a for which betainc(a, b, x) = p, or

\[p = \int_0^x \frac{\Gamma(a + b)}{\Gamma(a)\Gamma(b)} t^{a-1} (1-t)^{b-1}\,dt\]
Parameters:
parray_like

Cumulative probability, in [0, 1].

barray_like

Shape parameter (b > 0).

xarray_like

The quantile, in [0, 1].

outndarray, optional

Optional output array for the function values

Returns:
ascalar or ndarray

The value of the shape parameter a such that betainc(a, b, x) = p.

See also

betainc

Regularized incomplete beta function

betaincinv

Inverse of the regularized incomplete beta function

btdtrib

Inverse of the beta cumulative distribution function, with respect to b.

Notes

This function wraps the ibeta_inva routine from the Boost Math C++ library [1].

References

[1]

The Boost Developers. “Boost C++ Libraries”. https://www.boost.org/.

Examples

>>> import scipy.special as sc

This function is the inverse of betainc for fixed values of \(b\) and \(x\).

>>> a, b, x = 1.2, 3.1, 0.2
>>> y = sc.betainc(a, b, x)
>>> sc.btdtria(y, b, x)
1.2