the cumulative distribution function.  Must be in the
        range [0, 1].
    nc : array_like
        Noncentrality parameter.  Should be in range (0, 1e4).
    f : array_like
        Quantiles, i.e., the upper limit of integration.
    out : ndarray, optional
        Optional output array for the function results

    Returns
    -------
    dfd : scalar or ndarray
        Degrees of freedom of the denominator sum of squares.

    See Also
    --------
    ncfdtr : CDF of the non-central F distribution.
    ncfdtri : Quantile function; inverse of `ncfdtr` with respect to `f`.
    ncfdtridfn : Inverse of `ncfdtr` with respect to `dfn`.
    ncfdtrinc : Inverse of `ncfdtr` with respect to `nc`.

    Notes
    -----
    The value of the cumulative noncentral F distribution is not necessarily
    monotone in either degrees of freedom. There thus may be two values that
    provide a given CDF value. This routine assumes monotonicity and will
    find an arbitrary one of the two values.

    Examples
    --------
    >>> from scipy.special import ncfdtr, ncfdtridfd

    Compute the CDF for several values of `dfd`:

    >>> dfd = [1, 2, 3]
    >>> p = ncfdtr(2, dfd, 0.25, 15)
    >>> p
    array([ 0.8097138 ,  0.93020416,  0.96787852])

    Compute the inverse.  We recover the values of `dfd`, as expected:

    >>> ncfdtridfd(2, p, 0.25, 15)
    array([ 1.,  2.,  3.])

    Ú
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