add numerical recipes library

lib/nr/k_and_r/recipes/dftint.c

@@ -0,0 +1,65 @@
+
+#include <math.h>
+#include "nrutil.h"
+#define M 64
+#define NDFT 1024
+#define MPOL 6
+#define TWOPI (2.0*3.14159265)
+
+void dftint(func,a,b,w,cosint,sinint)
+float (*func)(),*cosint,*sinint,a,b,w;
+{
+	void dftcor(),polint(),realft();
+	static int init=0;
+	int j,nn;
+	static float aold = -1.e30,bold = -1.e30,delta,(*funcold)();
+	static float data[NDFT+1],endpts[9];
+	float c,cdft,cerr,corfac,corim,corre,en,s;
+	float sdft,serr,*cpol,*spol,*xpol;
+
+	cpol=vector(1,MPOL);
+	spol=vector(1,MPOL);
+	xpol=vector(1,MPOL);
+	if (init != 1 || a != aold || b != bold || func != funcold) {
+		init=1;
+		aold=a;
+		bold=b;
+		funcold=func;
+		delta=(b-a)/M;
+		for (j=1;j<=M+1;j++)
+			data[j]=(*func)(a+(j-1)*delta);
+		for (j=M+2;j<=NDFT;j++)
+			data[j]=0.0;
+		for (j=1;j<=4;j++) {
+			endpts[j]=data[j];
+			endpts[j+4]=data[M-3+j];
+		}
+		realft(data,NDFT,1);
+		data[2]=0.0;
+	}
+	en=w*delta*NDFT/TWOPI+1.0;
+	nn=IMIN(IMAX((int)(en-0.5*MPOL+1.0),1),NDFT/2-MPOL+1);
+	for (j=1;j<=MPOL;j++,nn++) {
+		cpol[j]=data[2*nn-1];
+		spol[j]=data[2*nn];
+		xpol[j]=nn;
+	}
+	polint(xpol,cpol,MPOL,en,&cdft,&cerr);
+	polint(xpol,spol,MPOL,en,&sdft,&serr);
+	dftcor(w,delta,a,b,endpts,&corre,&corim,&corfac);
+	cdft *= corfac;
+	sdft *= corfac;
+	cdft += corre;
+	sdft += corim;
+	c=delta*cos(w*a);
+	s=delta*sin(w*a);
+	*cosint=c*cdft-s*sdft;
+	*sinint=s*cdft+c*sdft;
+	free_vector(cpol,1,MPOL);
+	free_vector(spol,1,MPOL);
+	free_vector(xpol,1,MPOL);
+}
+#undef M
+#undef NDFT
+#undef MPOL
+#undef TWOPI