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# scipy.special.chndtridf

scipy.special.chndtridf(x, p, nc, out=None) = <ufunc 'chndtridf'>

  Inverse to `chndtr` vs df

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

  Parameters:
    x array_like

      Upper bound of the integral; must satisfy `x >= 0`

    p array_like

      Probability; must satisfy `0 <= p < 1`

    nc array_like

      Non-centrality parameter; must satisfy `nc >= 0`

    out ndarray, optional

      Optional output array for the function results

  Returns:
    df scalar or ndarray

      Degrees of freedom

  See also

  `chndtr`

    Noncentral chi-squared distribution CDF

  `chndtrix`

    inverse of `chndtr` with respect to x

  `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`.

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

  References

  [1]

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

  Examples

      >>> from scipy.special import chndtridf, chndtr

  Compute the noncentral chi squared distribution CDF at one point.

      >>> x, df, nc = 3, 5, 10
      >>> p = chndtr(x, df, nc)

  `chndtridf` is the inverse of `chndtr` with respect to df:

      >>> chndtridf(x, p, nc)
      5.0