add numerical recipes library

lib/nr/cpp/recipes/covsrt.cpp

@@ -0,0 +1,18 @@
+#include "nr.h"
+
+void NR::covsrt(Mat_IO_DP &covar, Vec_I_BOOL &ia, const int mfit)
+{
+	int i,j,k;
+
+	int ma=ia.size();
+	for (i=mfit;i<ma;i++)
+		for (j=0;j<i+1;j++) covar[i][j]=covar[j][i]=0.0;
+	k=mfit-1;
+	for (j=ma-1;j>=0;j--) {
+		if (ia[j]) {
+			for (i=0;i<ma;i++) SWAP(covar[i][k],covar[i][j]);
+			for (i=0;i<ma;i++) SWAP(covar[k][i],covar[j][i]);
+			k--;
+		}
+	}
+}