add numerical recipes library

lib/nr/cpp/recipes/interp.cpp

@@ -0,0 +1,17 @@
+#include "nr.h"
+
+void NR::interp(Mat_O_DP &uf, Mat_I_DP &uc)
+{
+	int ic,iif,jc,jf,nc;
+
+	int nf=uf.nrows();
+	nc=nf/2+1;
+	for (jc=0;jc<nc;jc++)
+		for (ic=0;ic<nc;ic++) uf[2*ic][2*jc]=uc[ic][jc];
+	for (jf=0;jf<nf;jf+=2)
+		for (iif=1;iif<nf-1;iif+=2)
+			uf[iif][jf]=0.5*(uf[iif+1][jf]+uf[iif-1][jf]);
+	for (jf=1;jf<nf-1;jf+=2)
+		for (iif=0;iif<nf;iif++)
+			uf[iif][jf]=0.5*(uf[iif][jf+1]+uf[iif][jf-1]);
+}