      ls=style)
    >>> ax.legend()
    >>> ax.set_ylabel("$k$")
    >>> ax.set_xlabel("$CDF$")
    >>> ax.set_title("Negative binomial percentile function")
    >>> plt.show()

    The negative binomial distribution is also available as
    `scipy.stats.nbinom`. The percentile function  method ``ppf``
    returns the result of `nbdtrik` rounded up to integers:

    >>> from scipy.stats import nbinom
    >>> q, n, p = 0.6, 5, 0.5
    >>> nbinom.ppf(q, n, p), nbdtrik(q, n, p)
    (5.0, 4.800428460273882)

    