add numerical recipes library

lib/nr/cpp/recipes/polcoe.cpp

@@ -0,0 +1,28 @@
+#include "nr.h"
+
+void NR::polcoe(Vec_I_DP &x, Vec_I_DP &y, Vec_O_DP &cof)
+{
+	int k,j,i;
+	DP phi,ff,b;
+
+	int n=x.size();
+	Vec_DP s(n);
+	for (i=0;i<n;i++) s[i]=cof[i]=0.0;
+	s[n-1]= -x[0];
+	for (i=1;i<n;i++) {
+		for (j=n-1-i;j<n-1;j++)
+			s[j] -= x[i]*s[j+1];
+		s[n-1] -= x[i];
+	}
+	for (j=0;j<n;j++) {
+		phi=n;
+		for (k=n-1;k>0;k--)
+			phi=k*s[k]+x[j]*phi;
+		ff=y[j]/phi;
+		b=1.0;
+		for (k=n-1;k>=0;k--) {
+			cof[k] += b*ff;
+			b=s[k]+x[j]*b;
+		}
+	}
+}