static int cdf_dchisq (lua_State *L) {
/* stack should contain x, df and opt. pnonc */
lua_Number x = luaL_checknumber(L, 1);
lua_Number df = luaL_checknumber(L, 2);
lua_Number pnonc = 0;
lua_Number d;
check_chisq(L, 1, x, df, pnonc);
/* compute central dchisq */
d = df/2;
d = exp((d-1)*log(x)-x/2-d*M_LN2-dlngam(&d));
lua_pushnumber(L, d);
return 1;
}
static int cdf_pchisq (lua_State *L) {
/* stack should contain x, df and opt. pnonc */
lua_Number x = luaL_checknumber(L, 1);
lua_Number df = luaL_checknumber(L, 2);
lua_Number pnonc = luaL_optnumber(L, 3, 0);
lua_Number p, q, bound;
int which = 1;
int status;
check_chisq(L, 1, x, df, pnonc);
if (pnonc==0) /* central? */
cdfchi(&which, &p, &q, &x, &df, &status, &bound);
else /* non-central */
cdfchn(&which, &p, &q, &x, &df, &pnonc, &status, &bound);
check_status(status, bound);
lua_pushnumber(L, p);
return 1;
}
static int stat_dchisq (lua_State *L) {
/* stack should contain x, df and opt. pnonc */
lua_Number x = luaL_checknumber(L, 1);
lua_Number df = luaL_checknumber(L, 2);
lua_Number pnonc = luaL_optnumber(L, 3, 0);
lua_Number d;
check_chisq(L, 1, x, df, pnonc);
/* compute central dchisq */
d = df / 2;
d = exp((d - 1) * log(x) - x / 2 - d * M_LN2 - dlngam(&d));
/* compute non-central if that's the case */
if (pnonc != 0) { /* non-central? */
/* evaluate weighted series */
int i;
lua_Number t = d *= exp(-pnonc / 2); /* first term */
for (i = 1; i < MAXITER && d > LBOUND && t > DBL_EPSILON * d; i++)
d += t *= x * pnonc / (2 * i * (df + 2 * (i - 1)));
}
lua_pushnumber(L, d);
return 1;
}
static int cdf_qchisq (lua_State *L) {
/* stack should contain p, df and opt. pnonc */
lua_Number p = luaL_checknumber(L, 1);
lua_Number df = luaL_checknumber(L, 2);
lua_Number pnonc = luaL_optnumber(L, 3, 0);
lua_Number x;
check_chisq(L, 2, p, df, pnonc);
if (p==0 || p==1) x = (p==0) ? 0 : HUGE_VAL;
else {
lua_Number q = 1-p;
lua_Number bound;
int which = 2;
int status;
if (pnonc==0) /* central? */
cdfchi(&which, &p, &q, &x, &df, &status, &bound);
else /* non-central */
cdfchn(&which, &p, &q, &x, &df, &pnonc, &status, &bound);
check_status(status, bound);
}
lua_pushnumber(L, x);
return 1;
}
