add numerical recipes library

lib/nr/cpp/recipes/splin2.cpp

@@ -0,0 +1,20 @@
+#include "nr.h"
+
+void NR::splin2(Vec_I_DP &x1a, Vec_I_DP &x2a, Mat_I_DP &ya, Mat_I_DP &y2a,
+	const DP x1, const DP x2, DP &y)
+{
+	int j,k;
+
+	int m=x1a.size();
+	int n=x2a.size();
+	Vec_DP ya_t(n),y2a_t(n),yytmp(m),ytmp(m);
+	for (j=0;j<m;j++) {
+		for (k=0;k<n;k++) {
+			ya_t[k]=ya[j][k];
+			y2a_t[k]=y2a[j][k];
+		}
+		splint(x2a,ya_t,y2a_t,x2,yytmp[j]);
+	}
+	spline(x1a,yytmp,1.0e30,1.0e30,ytmp);
+	splint(x1a,yytmp,ytmp,x1,y);
+}