Changeset 2382 for trunk/yat/statistics/Fisher.cc

Timestamp:

Dec 21, 2010, 2:16:58 PM (11 years ago)

Author:

Peter

Message:

merged patch release 0.6.3 into trunk.

Location:

trunk

Files:

• . (modified) (1 prop)
• yat/statistics/Fisher.cc (modified) (6 diffs)

trunk/yat/statistics/Fisher.cc

@@ -5 +5 @@
   Copyright (C) 2005 Peter Johansson
   Copyright (C) 2006, 2007, 2008 Jari Häkkinen, Peter Johansson
-  Copyright (C) 2009 Peter Johansson
+  Copyright (C) 2009, 2010 Peter Johansson
 
   This file is part of the yat library, http://dev.thep.lu.se/yat
@@ -32 +32 @@
 
 #include <algorithm>
+#include <cassert>
 
 namespace theplu {
@@ -66 +67 @@
   void Fisher::expected(double& a, double& b, double& c, double& d) const
   {
-    double N = a_+b_+c_+d_;
-    a =((a_+b_)*(a_+c_)) / N;
-    b =((a_+b_)*(b_+d_)) / N;
-    c =((c_+d_)*(a_+c_)) / N;
-    d =((c_+d_)*(b_+d_)) / N;
+    // use floting point arithmetic to avoid overflow
+    double a1 = a_;
+    double b1 = b_;
+    double c1 = c_;
+    double d1 = d_;
+    double N = a1 + b1 + c1 + d1;
+    a =((a1+b1)*(a1+c1)) / N;
+    b =((a1+b1)*(b1+d1)) / N;
+    c =((c1+d1)*(a1+c1)) / N;
+    d =((c1+d1)*(b1+d1)) / N;
   }
 
@@ -100 +106 @@
     d_ = d;
 
-    oddsratio_=static_cast<double>(a*d)/static_cast<double>(b*c);
+    oddsratio_= (static_cast<double>(a) / static_cast<double>(b) * 
+                 static_cast<double>(d) / static_cast<double>(c) );
     return oddsratio_;
   }
@@ -120 +127 @@
       return p_value_approximative()/2.0;
     }
+    // check for overflow
+    assert(c_ <= c_+d_ && d_ <= c_+d_);
+    assert(a_ <= a_+b_ && b_ <= a_+b_);
+    assert(a_ <= a_+c_ && c_ <= a_+c_);
+
     return statistics::cdf_hypergeometric_P(c_, c_+d_, a_+b_, a_+c_);
   }
@@ -149 +161 @@
   }
 
-
 }}} // of namespace statistics, yat, and theplu