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- /* cdf/fdist.c
- *
- * Copyright (C) 2002 Przemyslaw Sliwa and Jason H. Stover.
- * Copyright (C) 2006, 2007 Brian Gough
- *
- * 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 3 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, write to the Free Software
- * Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307, USA.
- */
- #include "gsl__config.h"
- #include <math.h>
- #include "gsl_cdf.h"
- #include "gsl_sf_gamma.h"
- #include "gsl_math.h"
- #include "gsl_errno.h"
- #include "gsl_cdf__error.h"
- #include "gsl_cdf__beta_inc.c"
- /*
- * Lower tail.
- */
- double
- gsl_cdf_fdist_P (const double x, const double nu1, const double nu2)
- {
- double P;
- double r = nu2 / nu1;
- if (x < r)
- {
- double u = x / (r + x);
- P = beta_inc_AXPY (1.0, 0.0, nu1 / 2.0, nu2 / 2.0, u);
- }
- else
- {
- double u = r / (r + x);
- P = beta_inc_AXPY (-1.0, 1.0, nu2 / 2.0, nu1 / 2.0, u);
- }
- return P;
- }
- /*
- * Upper tail.
- */
- double
- gsl_cdf_fdist_Q (const double x, const double nu1, const double nu2)
- {
- double Q;
- double r = nu2 / nu1;
- if (x < r)
- {
- double u = x / (r + x);
- Q = beta_inc_AXPY (-1.0, 1.0, nu1 / 2.0, nu2 / 2.0, u);
- }
- else
- {
- double u = r / (r + x);
- Q = beta_inc_AXPY (1.0, 0.0, nu2 / 2.0, nu1 / 2.0, u);
- }
- return Q;
- }
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