/*

 *  Mathlib : A C Library of Special Functions

 *  Copyright (C) 1998  Ross Ihaka

 *  Copyright (C) 2000-8 The R Core Team

 *

 *  This program is free software; you can redistribute it and/or modify

 *  it under the terms of the GNU General Public License as published by

 *  the Free Software Foundation; either version 2 of the License, or

 *  (at your option) any later version.

 *

 *  This program is distributed in the hope that it will be useful,

 *  but WITHOUT ANY WARRANTY; without even the implied warranty of

 *  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the

 *  GNU General Public License for more details.

 *

 *  You should have received a copy of the GNU General Public License

 *  along with this program; if not, a copy is available at

 *  https://www.R-project.org/Licenses/

 *

 *  DESCRIPTION

 *

 *  The distribution function of the non-central F distribution.

 */

#include "nmath.h"

#include "dpq.h"

double pnf(double x, double df1, double df2, double ncp,

     int lower_tail, int log_p)

{

    double y;

#ifdef IEEE_754

    if (ISNAN(x) || ISNAN(df1) || ISNAN(df2) || ISNAN(ncp))

  return x + df2 + df1 + ncp;

#endif

    if (df1 <= 0. || df2 <= 0. || ncp < 0) ML_WARN_return_NAN;

    if (!R_FINITE(ncp)) ML_WARN_return_NAN;

    if (!R_FINITE(df1) && !R_FINITE(df2)) /* both +Inf */

  ML_WARN_return_NAN;

    R_P_bounds_01(x, 0., ML_POSINF);

    if (df2 > 1e8) /* avoid problems with +Inf and loss of accuracy */

  return pnchisq(x * df1, df1, ncp, lower_tail, log_p);

    y = (df1 / df2) * x;

    return pnbeta2(y/(1. + y), 1./(1. + y), df1 / 2., df2 / 2.,

       ncp, lower_tail, log_p);

}