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/*
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/*
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 *  Mathlib : A C Library of Special Functions
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 *  Mathlib : A C Library of Special Functions
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 *  Copyright (C) 1998 Ross Ihaka
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 *  Copyright (C) 1998 Ross Ihaka
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 *  Copyright (C) 1999 R Core Team
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 *
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 *
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 *  This program is free software; you can redistribute it and/or modify
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 *  This program is free software; you can redistribute it and/or modify
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 *  it under the terms of the GNU General Public License as published by
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 *  it under the terms of the GNU General Public License as published by
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 *  the Free Software Foundation; either version 2 of the License, or
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 *  the Free Software Foundation; either version 2 of the License, or
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 *  (at your option) any later version.
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 *  (at your option) any later version.
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#include "Mathlib.h"
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#include "Mathlib.h"
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double phyper(double x, double NR, double NB, double n)
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double phyper(double x, double NR, double NB, double n)
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{
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{
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    double N, xstart, xend, xr, xb, sum, ltrm;
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/* Sample of  n balls from  NR red  and  NB black ones;  x are red */
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/* basically the same code is used also in  ./qhyper.c -- keep in sync! */
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    double N, xstart, xend, xr, xb, sum, term;
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    int small_N;
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#ifdef IEEE_754
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#ifdef IEEE_754
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    if(ISNAN(x) || ISNAN(NR) || ISNAN(NB) || ISNAN(n))
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    if(ISNAN(x) || ISNAN(NR) || ISNAN(NB) || ISNAN(n))
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	return x + NR + NB + n;
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	return x + NR + NB + n;
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    if(!finite(x) || !finite(NR) || !finite(NB) || !finite(n)) {
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    if(!finite(x) || !finite(NR) || !finite(NB) || !finite(n)) {
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	ML_ERROR(ME_DOMAIN);
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	ML_ERROR(ME_DOMAIN);
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    n = floor(n + 0.5);
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    n = floor(n + 0.5);
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    if (NR < 0 || NB < 0 || n < 0 || n > N) {
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    if (NR < 0 || NB < 0 || n < 0 || n > N) {
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	ML_ERROR(ME_DOMAIN);
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	ML_ERROR(ME_DOMAIN);
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	return ML_NAN;
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	return ML_NAN;
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    }
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    }
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    small_N = (N < 1000); /* won't have underflow in product below */
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    xstart = fmax2(0, n - NB);
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    xstart = fmax2(0, n - NB);
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    xend = fmin2(n, NR);
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    xend = fmin2(n, NR);
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    if(x < xstart) return 0.0;
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    if(x < xstart) return 0.0;
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    if(x >= xend) return 1.0;
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    if(x >= xend) return 1.0;
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    xr = xstart;
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    xr = xstart;
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    xb = n - xr;
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    xb = n - xr;
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    /* if N is small,  term := product.ratio( bin.coef );
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       otherwise work with its logarithm to protect against underflow */
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    ltrm = lfastchoose(NR, xr) + lfastchoose(NB, xb) - lfastchoose(N, n);
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    term = lfastchoose(NR, xr) + lfastchoose(NB, xb) - lfastchoose(N, n);
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    if(small_N) term = exp(term);
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    NR = NR - xr;
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    NR -= xr;
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    NB = NB - xb;
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    NB -= xb;
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    sum = 0.0;
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    sum = 0.0;
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    while(xr <= x) {
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    while(xr <= x) {
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	sum += exp(ltrm);
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	sum += (small_N ? term : exp(term));
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	xr++;
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	xr++;
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	NB++;
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	NB++;
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	if(small_N) term *= (NR / xr) * (xb / NB);
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	ltrm += log((NR / xr) * (xb / NB));
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	else	term += log((NR / xr) * (xb / NB));
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	xb--;
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	xb--;
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	NR--;
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	NR--;
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    }
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    }
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    return sum;
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    return sum;
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}
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}