

   TThhee FF DDiissttrriibbuuttiioonn

        df(x, n1, n2)
        pf(q, n1, n2)
        qf(p, n1, n2)
        rf(n, n1, n2)

   VVaalluuee::

        These functions provide information about the F distri-
        bution with `n1' and `n2' degrees of freedom.  `df'
        gives the density, `pf' gives the distribution function
        `qf' gives the quantile function and `rf' generates
        random deviates.

        The F distribution with n1 and n2 degrees of freedom
        has density

            f(x) =
            Gamma((n1 + n2)/2) / (Gamma(n1/2) Gamma(n2/2))
            (n1/n2)^(n1/2) x^(n1/2 - 1)
            (1 + (n1/n2) x)^-(n1 + n2)/2

        for x > 0.

   SSeeee AAllssoo::

        `dt' for Student's t distribution which is (almost)
        equivalent to `*f(..., n2 = 1)'.

   EExxaammpplleess::

        df(1,1,1) == dt(1,1)

