diggra.c
#include <R.h>
#include <Rmath.h>
#include <math.h>
#include "methas.h"
#include "dist2.h"
/* Conditional intensity computation for Diggle-Gratton process */
/*
Conditional intensity function for a pairwise interaction point
process with interaction function as given by
e(t) = 0 for t < delta
= (t-delta)/(rho-delta)^kappa for delta <= t < rho
= 1 for t >= rho
(See page 767 of Diggle, Gates, and Stibbard, Biometrika vol. 74,
1987, pages 763 -- 770.)
*/
/* Storage of parameters and precomputed/auxiliary data */
typedef struct Diggra {
double kappa;
double delta;
double rho;
double delta2; /* delta^2 */
double rho2; /* rho^2 */
double fac; /* 1/(rho-delta) */
double *period;
int per;
} Diggra;
/* initialiser function */
Cdata *diggrainit(state, model, algo)
State state;
Model model;
Algor algo;
{
Diggra *diggra;
diggra = (Diggra *) R_alloc(1, sizeof(Diggra));
/* Interpret model parameters*/
diggra->kappa = model.ipar[0];
diggra->delta = model.ipar[1];
diggra->rho = model.ipar[2];
diggra->period = model.period;
/* constants */
diggra->delta2 = pow(diggra->delta, 2);
diggra->rho2 = pow(diggra->rho, 2);
diggra->fac = 1/(diggra->rho - diggra->delta);
/* periodic boundary conditions? */
diggra->per = (model.period[0] > 0.0);
return((Cdata *) diggra);
}
/* conditional intensity evaluator */
double diggracif(prop, state, cdata)
Propo prop;
State state;
Cdata *cdata;
{
int npts, ix, ixp1, j;
double *x, *y;
double u, v;
double d2, pairprod, cifval;
double rho2, delta, delta2, fac;
double *period;
DECLARE_CLOSE_D2_VARS;
Diggra *diggra;
diggra = (Diggra *) cdata;
period = diggra->period;
rho2 = diggra->rho2;
delta = diggra->delta;
delta2 = diggra->delta2;
fac = diggra->fac;
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(diggra->per) { /* periodic distance */
if(ix > 0) {
for(j=0; j < ix; j++) {
if(CLOSE_PERIODIC_D2(u,v,x[j],y[j],period,rho2,d2)) {
if(d2 < delta2) {
cifval = 0.0;
return(cifval);
} else {
pairprod *= fac * (sqrt(d2)-delta);
}
}
}
}
if(ixp1 < npts) {
for(j=ixp1; j<npts; j++) {
if(CLOSE_PERIODIC_D2(u,v,x[j],y[j],period,rho2,d2)) {
if(d2 < delta2) {
cifval = 0.0;
return(cifval);
} else {
pairprod *= fac * (sqrt(d2)-delta);
}
}
}
}
} else { /* Euclidean distance */
if(ix > 0) {
for(j=0; j < ix; j++) {
if(CLOSE_D2(u, v, x[j], y[j], rho2, d2)) {
if(d2 <= delta2) {
cifval = 0.0;
return(cifval);
} else {
pairprod *= fac * (sqrt(d2)-delta);
}
}
}
}
if(ixp1 < npts) {
for(j=ixp1; j<npts; j++) {
if(CLOSE_D2(u, v, x[j], y[j], rho2, d2)) {
if(d2 <= delta2) {
cifval = 0.0;
return(cifval);
} else {
pairprod *= fac * (sqrt(d2)-delta);
}
}
}
}
}
cifval = pow(pairprod, diggra->kappa);
return cifval;
}
Cifns DiggraCifns = { &diggrainit, &diggracif, (updafunptr) NULL, NO};