scipy.special.chndtrix

scipy.special.chndtrix(p, df, nc, out=None) = <ufunc 'chndtrix'>

Inverse to chndtr vs x

Calculated using a search to find a value for x that produces the desired value of p.

Parameters:

parray_like

Probability; must satisfy 0 <= p < 1

dfarray_like

Degrees of freedom; must satisfy df > 0

ncarray_like

Non-centrality parameter; must satisfy nc >= 0

outndarray, optional

Optional output array for the function results

Returns:

xscalar or ndarray

Value so that the probability a non-central Chi square random variable with df degrees of freedom and non-centrality, nc, is greater than x equals p.

See also

chndtr

Noncentral chi-squared distribution CDF

chndtridf

inverse of chndtr with respect to cdf

chndtrinc

inverse of chndtr with respect to nc

scipy.stats.ncx2

Non-central chi-squared distribution

Notes

The noncentral chi squared distribution is also available in scipy.stats.ncx2. scipy.stats.ncx2.ppf is equivalent to chndtrix.

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

References

[1]

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

Examples

Try it in your browser!

>>> from scipy.special import chndtrix, chndtr

Compute the noncentral chi squared distribution CDF at one point. >>> x, df, nc = 3, 5, 10 >>> p = chndtr(x, df, nc)

chndtrix is the inverse of chndtr with respect to x:

>>> chndtrix(p, df, nc)
3.0

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