rnbinom.h

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// -*- mode: C++; c-indent-level: 4; c-basic-offset: 4; tab-width: 4 -*-
//
// rnbinom.h: Rcpp R/C++ interface class library -- 
//
// Copyright (C) 2010 - 2011 Douglas Bates, Dirk Eddelbuettel and Romain Francois
//
// This file is part of Rcpp.
//
// Rcpp 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.
//
// Rcpp 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 Rcpp.  If not, see <http://www.gnu.org/licenses/>.

#ifndef Rcpp__stats__random_rnbinom_h
#define Rcpp__stats__random_rnbinom_h

namespace Rcpp {
        namespace stats {

                class NBinomGenerator : public ::Rcpp::Generator<false,double> {
                public:
        
                        NBinomGenerator( double siz_, double prob_ ) : 
                                siz(siz_), lambda( (1-prob_)/prob_ ) {}
        
                        inline double operator()() const {
                                return ::Rf_rpois( ::Rf_rgamma( siz, lambda ) ) ; 
                        }
        
                private:
                        double siz ;
                        double lambda ;
                } ;
        } // stats

        // Please make sure you to read Section 6.3 of "Writing R Extensions"
        // about the need to call GetRNGstate() and PutRNGstate() when using 
        // the random number generators provided by R.
        inline NumericVector rnbinom( int n, double siz, double prob ){
                if(!R_FINITE(siz) || !R_FINITE(prob) || siz <= 0 || prob <= 0 || prob > 1)
                        /* prob = 1 is ok, PR#1218 */
                        return NumericVector( n, R_NaN ) ;
    
                return NumericVector( n, stats::NBinomGenerator( siz, prob ) ) ;
        }

} // Rcpp

#endif