##### https://github.com/cran/nacopula

Revision

**161411bb86f97e5a8bd89091cd61d03a33c2761a**authored by Martin Maechler on**06 February 2012, 00:00:00 UTC**, committed by Gabor Csardi on**06 February 2012, 00:00:00 UTC****1 parent**5bc804b

Tip revision:

**161411bb86f97e5a8bd89091cd61d03a33c2761a**authored by**Martin Maechler**on**06 February 2012, 00:00:00 UTC****version 0.8-0** Tip revision:

**161411b** unused.c

```
/*
Copyright (C) 2010 Marius Hofert and Martin Maechler
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, see <http://www.gnu.org/licenses/>.
*/
#include <Rmath.h>
#include "nacopula.h"
/**< lang5 will probably be defined in future versions of R */
#ifndef lang5
static SEXP lang5(SEXP s, SEXP t, SEXP u, SEXP v, SEXP w)
{
PROTECT(s);
s = LCONS(s, list4(t, u, v, w));
UNPROTECT(1);
return s;
}
#endif
/**
* This is really not useful, as the time is spent in the call to R's rstable1()
* Keep it as a didactical example of how to call R from C
* @param V vector of variables V01 (result)
* @param V0 vector of variates V0
* @param alpha parameter theta0/theta1 in (0,1]
* @param n number of variates V0, thus V01
* @return none
* @author Martin Maechler
*/
void C_retstable_R(double *V, const double V0[], double alpha, int n)
{
double c0 = cos(M_PI_2 * alpha);
SEXP one, alpha_R;
one = PROTECT(ScalarReal(1.));
alpha_R = PROTECT(ScalarReal(alpha));
GetRNGstate();
for(int i = 0; i < n; i++) {
/**< find m := optimal number of summands, using asymptotic formula */
double m = fmax(1., floor(0.5 + V0[i]));
/**
* Previously:
* double m;
* if(V0[i] <= 1)
* m= 1.;
* else {
* double fV= floor(V0[i]), cV= ceil(V0[i]);
* if(pow(exp(-V0[i]), 1./cV - 1./fV) <= cV/fV)
* m= fV;
* else
* m= cV;
* }
*/
/**< apply standard rejection m times */
SEXP gamma_, rstableCall;
PROTECT(gamma_ = ScalarReal(pow(c0*V0[i]/m, 1./alpha)));
PROTECT(rstableCall = lang5(install("rstable1"), one, /**< alpha= */
alpha_R, /**<beta= */ one, /**< gamma= */ gamma_));
for(int k= 0; k < m; k++) {
double V01_k, U;
/**< apply standard rejection */
do {
/**
* sample from the distribution corresponding to the
* Laplace-Stieltjes transform exp(-(V0/m)*t^alpha) via R
*/
V01_k = asReal(eval(rstableCall, R_GlobalEnv));
U = unif_rand();
} while (U > exp(- V01_k));
V[i] += V01_k;
}
UNPROTECT(2);
} /**< end for */
PutRNGstate();
UNPROTECT(1);
return;
}
```

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