add numerical recipes library

lib/nr/ansi/examples/xratlsq.c

@@ -0,0 +1,41 @@
+
+/* Driver for routine ratlsq */
+
+#include <stdio.h>
+#include <math.h>
+#define NRANSI
+#include "nr.h"
+#include "nrutil.h"
+
+#define NMAX 100
+
+double fn(double t)
+{
+	return atan(t);
+}
+
+int main(void)
+{
+	int j,kk,mm;
+	double a,b,*cof,dev,eee,fit,xs;
+
+	cof=dvector(0,NMAX);
+	for (;;) {
+		printf("enter a,b,mm,kk\n");
+		if (scanf("%lf %lf %d %d",&a,&b,&mm,&kk) == EOF) break;
+		ratlsq(fn,a,b,mm,kk,cof,&dev);
+		for (j=0;j<=mm+kk;j++) printf("cof(%3d)=%27.15e\n",j,cof[j]);
+		printf("maximum absolute deviation= %12.6f\n",dev);
+		printf("    x        error        exact\n");
+		printf("--------- ------------ ---------\n");
+		for (j=1;j<=50;j++) {
+			xs=a+(b-a)*(j-1.0)/49.0;
+			fit=ratval(xs,cof,mm,kk);
+			eee=fn(xs);
+			printf("%10.5f %15.7e %15.7e\n",xs,fit-eee,eee);
+		}
+	}
+	free_dvector(cof,0,NMAX);
+	return 0;
+}
+#undef NRANSI