void quadct(float x, float y, float xx[], float yy[], unsigned long nn,	float *fa, float *fb, float *fc, float *fd){	unsigned long k,na,nb,nc,nd;	float ff;	na=nb=nc=nd=0;	for (k=1;k<=nn;k++) {		if (yy[k] > y) {			xx[k] > x ? ++na : ++nb;		} else {			xx[k] > x ? ++nd : ++nc;		}	}	ff=1.0/nn;	*fa=ff*na;	*fb=ff*nb;	*fc=ff*nc;	*fd=ff*nd;}