add numerical recipes library

lib/nr/cpp/recipes/fixrts.cpp

@@ -0,0 +1,30 @@
+#include <cmath>
+#include <complex>
+#include "nr.h"
+using namespace std;
+
+void NR::fixrts(Vec_IO_DP &d)
+{
+	bool polish=true;
+	int i,j;
+
+	int m=d.size();
+	Vec_CPLX_DP a(m+1),roots(m);
+	a[m]=1.0;
+	for (j=0;j<m;j++)
+		a[j]= -d[m-1-j];
+	zroots(a,roots,polish);
+	for (j=0;j<m;j++)
+		if (abs(roots[j]) > 1.0)
+			roots[j]=1.0/conj(roots[j]);
+	a[0]= -roots[0];
+	a[1]=1.0;
+	for (j=1;j<m;j++) {
+		a[j+1]=1.0;
+		for (i=j;i>=1;i--)
+			a[i]=a[i-1]-roots[j]*a[i];
+		a[0]= -roots[j]*a[0];
+	}
+	for (j=0;j<m;j++)
+		d[m-1-j] = -real(a[j]);
+}