From 3705eb567bc624ec700a4e72d56cbe096bf91649 Mon Sep 17 00:00:00 2001
From: Sebastianw Wehling-Benatelli <sebastian.wehling@rub.de>
Date: Mon, 9 May 2016 12:06:47 +0200
Subject: [PATCH] [fix] overcome numerical instabilities

due to the usage of large absolute values (timestamp) on time axis the estimation of the expectation value gets instable
---
 pylot/core/util/pdf.py | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/pylot/core/util/pdf.py b/pylot/core/util/pdf.py
index 776192aa..1a233aed 100644
--- a/pylot/core/util/pdf.py
+++ b/pylot/core/util/pdf.py
@@ -256,9 +256,10 @@ class ProbabilityDensityFunction(object):
         '''
 
         rval = 0
-        for n, x in enumerate(self.axis):
+        axis = self.axis - self.x0
+        for n, x in enumerate(axis):
             rval += x * self.data[n]
-        return rval * self.incr
+        return rval * self.incr + self.x0
 
     def standard_deviation(self):
         mu = self.expectation()