add numerical recipes library

lib/nr/ansi/examples/xsplint.c

@@ -0,0 +1,65 @@
+
+/* Driver for routine splint */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define NP 10
+#define PI 3.1415926
+
+int main(void)
+{
+	int i,nfunc;
+	float f,x,y,yp1,ypn,*xa,*ya,*y2;
+
+	xa=vector(1,NP);
+	ya=vector(1,NP);
+	y2=vector(1,NP);
+	for (nfunc=1;nfunc<=2;nfunc++) {
+		if (nfunc == 1) {
+			printf("\nsine function from 0 to pi\n");
+			for (i=1;i<=NP;i++) {
+				xa[i]=i*PI/NP;
+				ya[i]=sin(xa[i]);
+			}
+			yp1=cos(xa[1]);
+			ypn=cos(xa[NP]);
+		} else if (nfunc == 2) {
+			printf("\nexponential function from 0 to 1\n");
+			for (i=1;i<=NP;i++) {
+				xa[i]=1.0*i/NP;
+				ya[i]=exp(xa[i]);
+			}
+			yp1=exp(xa[1]);
+			ypn=exp(xa[NP]);
+		} else {
+			break;
+		}
+		/* Call spline to get second derivatives */
+		spline(xa,ya,NP,yp1,ypn,y2);
+		/* Call splint for interpolations */
+		printf("\n%9s %13s %17s\n","x","f(x)","interpolation");
+		for (i=1;i<=10;i++) {
+			if (nfunc == 1) {
+				x=(-0.05+i/10.0)*PI;
+				f=sin(x);
+			} else if (nfunc == 2) {
+				x = -0.05+i/10.0;
+				f=exp(x);
+			}
+			splint(xa,ya,y2,NP,x,&y);
+			printf("%12.6f %12.6f %12.6f\n",x,f,y);
+		}
+		printf("\n***********************************\n");
+		printf("Press RETURN\n");
+		(void) getchar();
+	}
+	free_vector(y2,1,NP);
+	free_vector(ya,1,NP);
+	free_vector(xa,1,NP);
+	return 0;
+}
+#undef NRANSI