--- a
+++ b/inst/__incrementalRatio__.m
@@ -0,0 +1,24 @@
+## Copyright (C) 2008 simone pernice
+## 
+## This program is free software; you can redistribute it and/or modify
+## it under the terms of the GNU General Public License as published by
+## the Free Software Foundation; either version 2 of the License, or
+## (at your option) any later version.
+## 
+## This program is distributed in the hope that it will be useful,
+## but WITHOUT ANY WARRANTY; without even the implied warranty of
+## MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+## GNU General Public License for more details.
+## 
+## You should have received a copy of the GNU General Public License
+## along with this program; if not, write to the Free Software
+## Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301 USA
+
+## __incrementalRatio__ compute the incremental ratio of f(x) in x0 with dx2/2 delta
+
+## Author: simone pernice
+## Created: 2008-08-18
+
+function ret = __incrementalRatio__ (f, x0, dx2)
+  ret = (feval(f, x0+dx2)-feval(f, x0-dx2))/2/dx2;
+endfunction