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/* actuar: Actuarial Functions and Heavy Tailed Distributions
*
* Functions to compute density, cumulative distribution and quantile
* functions, raw and limited moments and to simulate random variates
* for the inverse Burr distribution. See ../R/InverseBurr.R for details.
*
* We work with the density expressed as
*
* shape1 * shape2 * u^shape1 * (1 - u) / x
*
* with u = v/(1 + v) = 1/(1 + 1/v), v = (x/scale)^shape2.
*
* AUTHORS: Mathieu Pigeon and Vincent Goulet <vincent.goulet@act.ulaval.ca>
*/
#include <R.h>
#include <Rmath.h>
#include "locale.h"
#include "dpq.h"
#include "actuar.h"
double dinvburr(double x, double shape1, double shape2, double scale,
int give_log)
{
#ifdef IEEE_754
if (ISNAN(x) || ISNAN(shape1) || ISNAN(shape2) || ISNAN(scale))
return x + shape1 + shape2 + scale;
#endif
if (!R_FINITE(shape1) ||
!R_FINITE(shape2) ||
shape1 <= 0.0 ||
shape2 <= 0.0 ||
scale <= 0.0)
return R_NaN;
if (!R_FINITE(x) || x < 0.0)
return ACT_D__0;
/* handle x == 0 separately */
if (x == 0.0)
{
if (shape1 * shape2 < 1) return R_PosInf;
if (shape1 * shape2 > 1) return ACT_D__0;
/* else */
return ACT_D_val(1.0/scale);
}
double logv, logu, log1mu;
logv = shape2 * (log(x) - log(scale));
logu = - log1pexp(-logv);
log1mu = - log1pexp(logv);
return ACT_D_exp(log(shape1) + log(shape2) + shape1 * logu
+ log1mu - log(x));
}
double pinvburr(double q, double shape1, double shape2, double scale,
int lower_tail, int log_p)
{
#ifdef IEEE_754
if (ISNAN(q) || ISNAN(shape1) || ISNAN(shape2) || ISNAN(scale))
return q + shape1 + shape2 + scale;
#endif
if (!R_FINITE(shape1) ||
!R_FINITE(shape2) ||
shape1 <= 0.0 ||
shape2 <= 0.0 ||
scale <= 0.0)
return R_NaN;
if (q <= 0)
return ACT_DT_0;
double u = exp(-log1pexp(shape2 * (log(scale) - log(q))));
return ACT_DT_val(R_pow(u, shape1));
}
double qinvburr(double p, double shape1, double shape2, double scale,
int lower_tail, int log_p)
{
#ifdef IEEE_754
if (ISNAN(p) || ISNAN(shape1) || ISNAN(shape2) || ISNAN(scale))
return p + shape1 + shape2 + scale;
#endif
if (!R_FINITE(shape1) ||
!R_FINITE(shape2) ||
!R_FINITE(scale) ||
shape1 <= 0.0 ||
shape2 <= 0.0 ||
scale <= 0.0)
return R_NaN;
ACT_Q_P01_boundaries(p, 0, R_PosInf);
p = ACT_D_qIv(p);
return scale * R_pow(R_pow(ACT_D_Lval(p), -1.0/shape1) - 1.0, -1.0/shape2);
}
double rinvburr(double shape1, double shape2, double scale)
{
if (!R_FINITE(shape1) ||
!R_FINITE(shape2) ||
!R_FINITE(scale) ||
shape1 <= 0.0 ||
shape2 <= 0.0 ||
scale <= 0.0)
return R_NaN;
return scale * R_pow(R_pow(unif_rand(), -1.0/shape1) - 1.0, -1.0/shape2);
}
double minvburr(double order, double shape1, double shape2, double scale,
int give_log)
{
#ifdef IEEE_754
if (ISNAN(order) || ISNAN(shape1) || ISNAN(shape2) || ISNAN(scale))
return order + shape1 + shape2 + scale;
#endif
if (!R_FINITE(shape1) ||
!R_FINITE(shape2) ||
!R_FINITE(scale) ||
!R_FINITE(order) ||
shape1 <= 0.0 ||
shape2 <= 0.0 ||
scale <= 0.0)
return R_NaN;
if (order <= - shape1 * shape2 ||
order >= shape2)
return R_PosInf;
double tmp = order / shape2;
return R_pow(scale, order) * gammafn(shape1 + tmp) * gammafn(1.0 - tmp)
/ gammafn(shape1);
}
double levinvburr(double limit, double shape1, double shape2, double scale,
double order, int give_log)
{
#ifdef IEEE_754
if (ISNAN(limit) || ISNAN(shape1) || ISNAN(shape2) || ISNAN(scale) || ISNAN(order))
return limit + shape1 + shape2 + scale + order;
#endif
if (!R_FINITE(shape1) ||
!R_FINITE(shape2) ||
!R_FINITE(scale) ||
!R_FINITE(order) ||
shape1 <= 0.0 ||
shape2 <= 0.0 ||
scale <= 0.0)
return R_NaN;
if (order <= -shape1 * shape2)
return R_PosInf;
if (limit <= 0.0)
return 0.0;
double logv, u, u1m;
double tmp = order / shape2;
logv = shape2 * (log(limit) - log(scale));
u = exp(-log1pexp(-logv));
u1m = exp(-log1pexp(logv));
return R_pow(scale, order)
* betaint_raw(u, shape1 + tmp, 1.0 - tmp, u1m)
/ gammafn(shape1)
+ ACT_DLIM__0(limit, order) * (0.5 - R_pow(u, shape1) + 0.5);
}
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