dgs.c
#include <R.h>
#include <Rmath.h>
#include <math.h>
#include "methas.h"
#include "dist2.h"
#include "constants.h"
/* Conditional intensity computation for Diggle-Gates-Stibbard process */
/*
Conditional intensity function for a pairwise interaction point
process with interaction function as given by
e(t) = sin^2(pi*t/2*rho) for t < rho
= 1 for t >= rho
(See page 767 of Diggle, Gates, and Stibbard, Biometrika vol. 74,
1987, pages 763 -- 770.)
*/
#define PION2 M_PI_2 /* pi/2 defined in Rmath.h */
/* Storage of parameters and precomputed/auxiliary data */
typedef struct Dgs {
double rho;
double rho2;
double pion2rho;
double *period;
int per;
} Dgs;
/* initialiser function */
Cdata *dgsinit(state, model, algo)
State state;
Model model;
Algor algo;
{
Dgs *dgs;
/* allocate storage */
dgs = (Dgs *) R_alloc(1, sizeof(Dgs));
/* Interpret model parameters*/
dgs->rho = model.ipar[0];
dgs->period = model.period;
/* constants */
dgs->rho2 = pow(dgs->rho, 2);
dgs->pion2rho = PION2/dgs->rho;
/* periodic boundary conditions? */
dgs->per = (model.period[0] > 0.0);
return((Cdata *) dgs);
}
/* conditional intensity evaluator */
double dgscif(prop, state, cdata)
Propo prop;
State state;
Cdata *cdata;
{
int npts, ix, ixp1, j;
double *x, *y;
double u, v;
double d2, r2, pairprod, cifval;
Dgs *dgs;
DECLARE_CLOSE_D2_VARS;
dgs = (Dgs *) cdata;
r2 = dgs->rho2;
u = prop.u;
v = prop.v;
ix = prop.ix;
x = state.x;
y = state.y;
npts = state.npts;
cifval = pairprod = 1.0;
if(npts == 0)
return(cifval);
ixp1 = ix+1;
/* If ix = NONE = -1, then ixp1 = 0 is correct */
if(dgs->per) { /* periodic distance */
if(ix > 0) {
for(j=0; j < ix; j++) {
if(CLOSE_PERIODIC_D2(u,v,x[j],y[j],dgs->period,r2,d2))
pairprod *= sin(dgs->pion2rho * sqrt(d2));
}
}
if(ixp1 < npts) {
for(j=ixp1; j<npts; j++) {
if(CLOSE_PERIODIC_D2(u,v,x[j],y[j],dgs->period,r2,d2))
pairprod *= sin(dgs->pion2rho * sqrt(d2));
}
}
}
else { /* Euclidean distance */
if(ix > 0) {
for(j=0; j < ix; j++) {
if(CLOSE_D2(u, v, x[j], y[j], r2, d2))
pairprod *= sin(dgs->pion2rho * sqrt(d2));
}
}
if(ixp1 < npts) {
for(j=ixp1; j<npts; j++) {
if(CLOSE_D2(u, v, x[j], y[j], r2, d2))
pairprod *= sin(dgs->pion2rho * sqrt(d2));
}
}
}
/* sin to sin^2 */
cifval = pairprod * pairprod;
return cifval;
}
Cifns DgsCifns = { &dgsinit, &dgscif, (updafunptr) NULL, NO};