add numerical recipes library

lib/nr/cpp/recipes/quadct.cpp

@@ -0,0 +1,22 @@
+#include "nr.h"
+
+void NR::quadct(const DP x, const DP y, Vec_I_DP &xx, Vec_I_DP &yy, DP &fa,
+	DP &fb, DP &fc, DP &fd)
+{
+	int k,na,nb,nc,nd;
+	DP ff;
+
+	int nn=xx.size();
+	na=nb=nc=nd=0;
+	for (k=0;k<nn;k++) {
+		if (yy[k] > y)
+			xx[k] > x ? ++na : ++nb;
+		else
+			xx[k] > x ? ++nd : ++nc;
+	}
+	ff=1.0/nn;
+	fa=ff*na;
+	fb=ff*nb;
+	fc=ff*nc;
+	fd=ff*nd;
+}