add numerical recipes library

lib/nr/k_and_r/recipes/rebin.c

@@ -0,0 +1,19 @@
+
+void rebin(rc,nd,r,xin,xi)
+float r[],rc,xi[],xin[];
+int nd;
+{
+	int i,k=0;
+	float dr=0.0,xn=0.0,xo=0.0;
+
+	for (i=1;i<nd;i++) {
+		while (rc > dr)
+			dr += r[++k];
+		if (k > 1) xo=xi[k-1];
+		xn=xi[k];
+		dr -= rc;
+		xin[i]=xn-(xn-xo)*dr/r[k];
+	}
+	for (i=1;i<nd;i++) xi[i]=xin[i];
+	xi[nd]=1.0;
+}