double dbinom_raw(double x, double n, double p, double q, int give_log)
{
double lf, lc;
if (p == 0) return((x == 0) ? R_D__1 : R_D__0);
if (q == 0) return((x == n) ? R_D__1 : R_D__0);
if (x == 0) {
if(n == 0) return R_D__1;
lc = (p < 0.1) ? -bd0(n,n*q) - n*p : n*log(q);
return( R_D_exp(lc) );
}
if (x == n) {
lc = (q < 0.1) ? -bd0(n,n*p) - n*q : n*log(p);
return( R_D_exp(lc) );
}
if (x < 0 || x > n) return( R_D__0 );
/* n*p or n*q can underflow to zero if n and p or q are small. This
used to occur in dbeta, and gives NaN as from R 2.3.0. */
lc = stirlerr(n) - stirlerr(x) - stirlerr(n-x) - bd0(x,n*p) - bd0(n-x,n*q);
/* f = (M_2PI*x*(n-x))/n; could overflow or underflow */
/* Upto R 2.7.1:
* lf = log(M_2PI) + log(x) + log(n-x) - log(n);
* -- following is much better for x << n : */
lf = M_LN_2PI + log(x) + log1p(- x/n);
return R_D_exp(lc - 0.5*lf);
}
double dbinom(int x, int n, double p)
{
assert((p>=0) && (p<=1));
assert(n>=0);
assert((x>=0) && (x<=n));
if (p==0.0) return x==0 ? 1.0 : 0.0;
if (p==1.0) return x==n ? 1.0 : 0.0;
if (x==0) return exp(n*log(1-p));
if (x==n) return exp(n*log(p));
double lc = stirlerr(n) - stirlerr(x) - stirlerr(n-x) - bd0(x, n*p) - bd0(n-x, n*(1-p));
return exp(lc)*sqrt(n/(PI2*x*(n-x)));
}
static lua_Number dbinom_raw (lua_Number x, lua_Number n, lua_Number p,
lua_Number q) {
lua_Number f, lc;
if (p == 0) return (x == 0) ? 1 : 0;
if (q == 0) return (x == n) ? 1 : 0;
if (x == 0)
return exp((p < 0.1) ? -bd0(n, n * q) - n * p : n * log(q));
if (x == n)
return exp((q < 0.1) ? -bd0(n, n * p) - n * q : n * log(p));
if ((x < 0) || (x > n)) return 0;
lc = stirlerr(n) - stirlerr(x) - stirlerr(n - x)
- bd0(x, n * p) - bd0(n - x, n * q);
f = (2 * M_PI * x * (n - x)) / n;
return exp(lc) / sqrt(f);
}
double dt(double x, double n, int give_log)
{
#ifdef IEEE_754
if (ISNAN(x) || ISNAN(n))
return x + n;
#endif
if (n <= 0) ML_ERR_return_NAN;
if(!R_FINITE(x))
return R_D__0;
if(!R_FINITE(n))
return dnorm(x, 0., 1., give_log);
double u, ax, t = -bd0(n/2.,(n+1)/2.) + stirlerr((n+1)/2.) - stirlerr(n/2.),
x2n = x*x/n, // in [0, Inf]
l_x2n; // := log(sqrt(1 + x2n)) = log(1 + x2n)/2
Rboolean lrg_x2n = (x2n > 1./DBL_EPSILON);
if (lrg_x2n) { // large x^2/n :
ax = fabs(x);
l_x2n = log(ax) - log(n)/2.; // = log(x2n)/2 = 1/2 * log(x^2 / n)
u = // log(1 + x2n) * n/2 = n * log(1 + x2n)/2 =
n * l_x2n;
}
else if (x2n > 0.2) {
l_x2n = log(1 + x2n)/2.;
u = n * l_x2n;
} else {
l_x2n = log1p(x2n)/2.;
u = -bd0(n/2.,(n+x*x)/2.) + x*x/2.;
}
//old: return R_D_fexp(M_2PI*(1+x2n), t-u);
// R_D_fexp(f,x) := (give_log ? -0.5*log(f)+(x) : exp(x)/sqrt(f))
// f = 2pi*(1+x2n)
// ==> 0.5*log(f) = log(2pi)/2 + log(1+x2n)/2 = log(2pi)/2 + l_x2n
// 1/sqrt(f) = 1/sqrt(2pi * (1+ x^2 / n))
// = 1/sqrt(2pi)/(|x|/sqrt(n)*sqrt(1+1/x2n))
// = M_1_SQRT_2PI * sqrt(n)/ (|x|*sqrt(1+1/x2n))
if(give_log)
return t-u - (M_LN_SQRT_2PI + l_x2n);
// else : if(lrg_x2n) : sqrt(1 + 1/x2n) ='= sqrt(1) = 1
double I_sqrt_ = (lrg_x2n ? sqrt(n)/ax : exp(-l_x2n));
return exp(t-u) * M_1_SQRT_2PI * I_sqrt_;
}
double dpois_raw(NMATH_STATE *state, double x, double lambda, int give_log)
{
/* x >= 0 ; integer for dpois(), but not e.g. for pgamma()!
lambda >= 0
*/
if (lambda == 0) return( (x == 0) ? R_D__1 : R_D__0 );
if (!isfinite(lambda)) return R_D__0;
if (x < 0) return( R_D__0 );
if (x <= lambda * DBL_MIN) return(R_D_exp(-lambda) );
if (lambda < x * DBL_MIN) return(R_D_exp(-lambda + x*log(lambda) -lgammafn(state, x+1)));
return(R_D_fexp( M_PI*2.0*x, -stirlerr(state,x)-bd0(x,lambda) ));
}
double attribute_hidden dpois_raw(double x, double lambda, int give_log)
{
/* x >= 0 ; integer for dpois(), but not e.g. for pgamma()!
lambda >= 0
*/
if (lambda == 0) return( (x == 0) ? R_D__1 : R_D__0 );
if (!R_FINITE(lambda)) return R_D__0;
if (x < 0) return( R_D__0 );
if (x <= lambda * DBL_MIN) return(R_D_exp(-lambda) );
if (lambda < x * DBL_MIN) return(R_D_exp(-lambda + x*log(lambda) -lgammafn(x+1)));
return(R_D_fexp( M_2PI*x, -stirlerr(x)-bd0(x,lambda) ));
}
double gammafn(double x)
{
const static double gamcs[42] = {
+.8571195590989331421920062399942e-2,
+.4415381324841006757191315771652e-2,
+.5685043681599363378632664588789e-1,
-.4219835396418560501012500186624e-2,
+.1326808181212460220584006796352e-2,
-.1893024529798880432523947023886e-3,
+.3606925327441245256578082217225e-4,
-.6056761904460864218485548290365e-5,
+.1055829546302283344731823509093e-5,
-.1811967365542384048291855891166e-6,
+.3117724964715322277790254593169e-7,
-.5354219639019687140874081024347e-8,
+.9193275519859588946887786825940e-9,
-.1577941280288339761767423273953e-9,
+.2707980622934954543266540433089e-10,
-.4646818653825730144081661058933e-11,
+.7973350192007419656460767175359e-12,
-.1368078209830916025799499172309e-12,
+.2347319486563800657233471771688e-13,
-.4027432614949066932766570534699e-14,
+.6910051747372100912138336975257e-15,
-.1185584500221992907052387126192e-15,
+.2034148542496373955201026051932e-16,
-.3490054341717405849274012949108e-17,
+.5987993856485305567135051066026e-18,
-.1027378057872228074490069778431e-18,
+.1762702816060529824942759660748e-19,
-.3024320653735306260958772112042e-20,
+.5188914660218397839717833550506e-21,
-.8902770842456576692449251601066e-22,
+.1527474068493342602274596891306e-22,
-.2620731256187362900257328332799e-23,
+.4496464047830538670331046570666e-24,
-.7714712731336877911703901525333e-25,
+.1323635453126044036486572714666e-25,
-.2270999412942928816702313813333e-26,
+.3896418998003991449320816639999e-27,
-.6685198115125953327792127999999e-28,
+.1146998663140024384347613866666e-28,
-.1967938586345134677295103999999e-29,
+.3376448816585338090334890666666e-30,
-.5793070335782135784625493333333e-31
};
int i, n;
double y;
double sinpiy, value;
#ifdef NOMORE_FOR_THREADS
static int ngam = 0;
static double xmin = 0, xmax = 0., xsml = 0., dxrel = 0.;
/* Initialize machine dependent constants, the first time gamma() is called.
FIXME for threads ! */
if (ngam == 0) {
ngam = chebyshev_init(gamcs, 42, DBL_EPSILON/20);/*was .1*d1mach(3)*/
gammalims(&xmin, &xmax);/*-> ./gammalims.c */
xsml = exp(fmax2(log(DBL_MIN), -log(DBL_MAX)) + 0.01);
/* = exp(.01)*DBL_MIN = 2.247e-308 for IEEE */
dxrel = sqrt(DBL_EPSILON);/*was sqrt(d1mach(4)) */
}
#else
/* For IEEE double precision DBL_EPSILON = 2^-52 = 2.220446049250313e-16 :
* (xmin, xmax) are non-trivial, see ./gammalims.c
* xsml = exp(.01)*DBL_MIN
* dxrel = sqrt(DBL_EPSILON) = 2 ^ -26
*/
# define ngam 22
# define xmin -170.5674972726612
# define xmax 171.61447887182298
# define xsml 2.2474362225598545e-308
# define dxrel 1.490116119384765696e-8
#endif
if(ISNAN(x)) return x;
/* If the argument is exactly zero or a negative integer
* then return NaN. */
if (x == 0 || (x < 0 && x == (long)x)) {
ML_ERROR(ME_DOMAIN, "gammafn");
return ML_NAN;
}
y = fabs(x);
if (y <= 10) {
/* Compute gamma(x) for -10 <= x <= 10
* Reduce the interval and find gamma(1 + y) for 0 <= y < 1
* first of all. */
n = (int) x;
if(x < 0) --n;
y = x - n;/* n = floor(x) ==> y in [ 0, 1 ) */
--n;
value = chebyshev_eval(y * 2 - 1, gamcs, ngam) + .9375;
if (n == 0)
return value;/* x = 1.dddd = 1+y */
if (n < 0) {
/* compute gamma(x) for -10 <= x < 1 */
/* exact 0 or "-n" checked already above */
/* The answer is less than half precision */
/* because x too near a negative integer. */
if (x < -0.5 && fabs(x - (int)(x - 0.5) / x) < dxrel) {
ML_ERROR(ME_PRECISION, "gammafn");
}
/* The argument is so close to 0 that the result would overflow. */
if (y < xsml) {
ML_ERROR(ME_RANGE, "gammafn");
if(x > 0) return ML_POSINF;
else return ML_NEGINF;
}
n = -n;
for (i = 0; i < n; i++) {
value /= (x + i);
}
return value;
}
else {
/* gamma(x) for 2 <= x <= 10 */
for (i = 1; i <= n; i++) {
value *= (y + i);
}
return value;
}
}
else {
/* gamma(x) for y = |x| > 10. */
if (x > xmax) { /* Overflow */
ML_ERROR(ME_RANGE, "gammafn");
return ML_POSINF;
}
if (x < xmin) { /* Underflow */
ML_ERROR(ME_UNDERFLOW, "gammafn");
return 0.;
}
if(y <= 50 && y == (int)y) { /* compute (n - 1)! */
value = 1.;
for (i = 2; i < y; i++) value *= i;
}
else { /* normal case */
value = exp((y - 0.5) * log(y) - y + M_LN_SQRT_2PI +
((2*y == (int)2*y)? stirlerr(y) : lgammacor(y)));
}
if (x > 0)
return value;
if (fabs((x - (int)(x - 0.5))/x) < dxrel){
/* The answer is less than half precision because */
/* the argument is too near a negative integer. */
ML_ERROR(ME_PRECISION, "gammafn");
}
sinpiy = sin(M_PI * y);
if (sinpiy == 0) { /* Negative integer arg - overflow */
ML_ERROR(ME_RANGE, "gammafn");
return ML_POSINF;
}
return -M_PI / (y * sinpiy * value);
}
}
double dpois(int x, double lb)
{
if (lb==0.0) return x==0 ? 1.0 : 0.0;
if (x==0) return exp(-lb);
return exp(-stirlerr(x)-bd0(x,lb))/sqrt(PI2*x);
}
gnm_float
pst (gnm_float x, gnm_float n, gnm_float shape, gboolean lower_tail, gboolean log_p)
{
gnm_float p;
if (n <= 0 || gnm_isnan (x) || gnm_isnan (n) || gnm_isnan (shape))
return gnm_nan;
if (shape == 0.)
return pt (x, n, lower_tail, log_p);
if (n > 100) {
/* Approximation */
return psnorm (x, shape, 0.0, 1.0, lower_tail, log_p);
}
/* Flip to a lower-tail problem. */
if (!lower_tail) {
x = -x;
shape = -shape;
lower_tail = !lower_tail;
}
/* Generic fallback. */
if (log_p)
gnm_log (pst (x, n, shape, TRUE, FALSE));
if (n != gnm_floor (n)) {
/* We would need numerical integration for this. */
return gnm_nan;
}
/*
* Use recurrence formula from "Recurrent relations for
* distributions of a skew-t and a linear combination of order
* statistics form a bivariate-t", Computational Statistics
* and Data Analysis volume 52, 2009 by Jamallizadeh,
* Khosravi, Balakrishnan.
*
* This brings us down to n==1 or n==2 for which explicit formulas
* are available.
*/
p = 0;
while (n > 2) {
double a, lb, c, d, pv, v = n - 1;
d = v == 2
? M_LN2gnum - gnm_log (M_PIgnum) + gnm_log (3) / 2
: (0.5 + M_LN2gnum / 2 - gnm_log (M_PIgnum) / 2 +
v / 2 * (gnm_log1p (-1 / (v - 1)) + gnm_log (v + 1)) -
0.5 * (gnm_log (v - 2) + gnm_log (v + 1)) +
stirlerr (v / 2 - 1) -
stirlerr ((v - 1) / 2));
a = v + 1 + x * x;
lb = (d - gnm_log (a) * v / 2);
c = pt (gnm_sqrt (v) * shape * x / gnm_sqrt (a), v, TRUE, FALSE);
pv = x * gnm_exp (lb) * c;
p += pv;
n -= 2;
x *= gnm_sqrt ((v - 1) / (v + 1));
}
g_return_val_if_fail (n == 1 || n == 2, gnm_nan);
if (n == 1) {
gnm_float p1;
p1 = (gnm_atan (x) + gnm_acos (shape / gnm_sqrt ((1 + shape * shape) * (1 + x * x)))) / M_PIgnum;
p += p1;
} else if (n == 2) {
gnm_float p2, f;
f = x / gnm_sqrt (2 + x * x);
p2 = (gnm_atan_mpihalf (shape) + f * gnm_atan_mpihalf (-shape * f)) / -M_PIgnum;
p += p2;
} else {
return gnm_nan;
}
/*
* Negatives can occur due to rounding errors and hopefully for no
* other reason.
*/
p = CLAMP (p, 0.0, 1.0);
return p;
}
