add numerical recipes library

lib/nr/ansi/examples/xpade.c

@@ -0,0 +1,51 @@
+
+/* Driver for routine pade */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+double fn(double x)
+{
+	return (x == 0.0 ? 1.0 : log(1.0+x)/x);
+}
+
+#define NMAX 100
+
+int main(void)
+{
+	int j,k,n;
+	float resid;
+	double b,d,fac,x,*c,*cc;
+
+	c=dvector(0,NMAX);
+	cc=dvector(0,NMAX);
+	for (;;) {
+		printf("Enter n for PADE routine:\n");
+		if (scanf("%d",&n) == EOF) break;
+		fac=1;
+		for (j=1;j<=2*n+1;j++) {
+			c[j-1]=fac/((double) j);
+			cc[j-1]=c[j-1];
+			fac = -fac;
+		}
+		pade(c,n,&resid);
+		printf("Norm of residual vector= %16.8e\n",resid);
+		printf("point, func. value, pade series, power series\n");
+		for (j=1;j<=21;j++) {
+			x=(j-1)*0.25;
+			for (b=0.0,k=2*n+1;k>=1;k--) {
+				b *= x;
+				b += cc[k-1];
+			}
+			d=ratval(x,c,n,n);
+			printf("%16.8f %16.8f %16.8f %16.8f\n",x,fn(x),d,b);
+		}
+	}
+	free_dvector(cc,0,NMAX);
+	free_dvector(c,0,NMAX);
+	return 0;
+}
+#undef NRANSI