add numerical recipes library

lib/nr/cpp/recipes/polcof.cpp

@@ -0,0 +1,38 @@
+#include <cmath>
+#include "nr.h"
+using namespace std;
+
+void NR::polcof(Vec_I_DP &xa, Vec_I_DP &ya, Vec_O_DP &cof)
+{
+	int k,j,i;
+	DP xmin,dy;
+
+	int n=xa.size();
+	Vec_DP x(n),y(n);
+	for (j=0;j<n;j++) {
+		x[j]=xa[j];
+		y[j]=ya[j];
+	}
+	for (j=0;j<n;j++) {
+		Vec_DP x_t(n-j),y_t(n-j);
+		for (k=0;k<n-j;k++) {
+			x_t[k]=x[k];
+			y_t[k]=y[k];
+		}
+		polint(x_t,y_t,0.0,cof[j],dy);
+		xmin=1.0e38;
+		k = -1;
+		for (i=0;i<n-j;i++) {
+			if (fabs(x[i]) < xmin) {
+				xmin=fabs(x[i]);
+				k=i;
+			}
+			if (x[i] != 0.0)
+				y[i]=(y[i]-cof[j])/x[i];
+		}
+		for (i=k+1;i<n-j;i++) {
+			y[i-1]=y[i];
+			x[i-1]=x[i];
+		}
+	}
+}