| /* |
| * Mathlib : A C Library of Special Functions |
| * Copyright (C) 1998 Ross Ihaka |
| * Copyright (C) 2000-2014 The R Core Team |
| * Copyright (C) 2004 The R Foundation |
| * |
| * 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 Cauchy distribution. |
| */ |
| |
| #include <config.h> |
| |
| #ifdef HAVE_ATANPI |
| double atanpi(double); |
| #endif |
| |
| #include "nmath.h" |
| #include "dpq.h" |
| |
| double pcauchy(double x, double location, double scale, |
| int lower_tail, int log_p) |
| { |
| #ifdef IEEE_754 |
| if (ISNAN(x) || ISNAN(location) || ISNAN(scale)) |
| return x + location + scale; |
| #endif |
| if (scale <= 0) ML_ERR_return_NAN; |
| |
| x = (x - location) / scale; |
| if (ISNAN(x)) ML_ERR_return_NAN; |
| #ifdef IEEE_754 |
| if(!R_FINITE(x)) { |
| if(x < 0) return R_DT_0; |
| else return R_DT_1; |
| } |
| #endif |
| if (!lower_tail) |
| x = -x; |
| /* for large x, the standard formula suffers from cancellation. |
| * This is from Morten Welinder thanks to Ian Smith's atan(1/x) : */ |
| #ifdef HAVE_ATANPI |
| if (fabs(x) > 1) { |
| double y = atanpi(1/x); |
| return (x > 0) ? R_D_Clog(y) : R_D_val(-y); |
| } else |
| return R_D_val(0.5 + atanpi(x)); |
| #else |
| if (fabs(x) > 1) { |
| double y = atan(1/x) / M_PI; |
| return (x > 0) ? R_D_Clog(y) : R_D_val(-y); |
| } else |
| return R_D_val(0.5 + atan(x) / M_PI); |
| #endif |
| } |