From: pbristow_at_[hidden]
Date: 2008-02-16 05:36:02
Author: pbristow
Date: 2008-02-16 05:36:02 EST (Sat, 16 Feb 2008)
New Revision: 43275
URL: http://svn.boost.org/trac/boost/changeset/43275
Log:
Corrected range to permit df == 2
and Added comment(-ed code) about mode with df < 2.
No reply to question about this on Wikipedia 16 Feb 08.
Text files modified:
sandbox/math_toolkit/boost/math/distributions/chi_squared.hpp | 18 +++++++++++++++---
1 files changed, 15 insertions(+), 3 deletions(-)
Modified: sandbox/math_toolkit/boost/math/distributions/chi_squared.hpp
==============================================================================
--- sandbox/math_toolkit/boost/math/distributions/chi_squared.hpp (original)
+++ sandbox/math_toolkit/boost/math/distributions/chi_squared.hpp 2008-02-16 05:36:02 EST (Sat, 16 Feb 2008)
@@ -1,5 +1,5 @@
// Copyright John Maddock 2006, 2007.
-// Copyright Paul A. Bristow 2007.
+// Copyright Paul A. Bristow 2008.
// Use, modification and distribution are subject to the
// Boost Software License, Version 1.0.
@@ -202,10 +202,22 @@
{
RealType df = dist.degrees_of_freedom();
static const char* function = "boost::math::mode(const chi_squared_distribution<%1%>&)";
- if(df <= 2)
+ // Most sources only define mode for df >= 2,
+ // but for 0 <= df <= 2, the pdf maximum actually occurs at random variate = 0;
+ // So one could extend the definition of mode thus:
+ //if(df < 0)
+ //{
+ // return policies::raise_domain_error<RealType>(
+ // function,
+ // "Chi-Squared distribution only has a mode for degrees of freedom >= 0, but got degrees of freedom = %1%.",
+ // df, Policy());
+ //}
+ //return (df <= 2) ? 0 : df - 2;
+
+ if(df < 2)
return policies::raise_domain_error<RealType>(
function,
- "The Chi-Squared distribution only has a mode for degrees of freedom >= 2, but got degrees of freedom = %1%.",
+ "Chi-Squared distribution only has a mode for degrees of freedom >= 2, but got degrees of freedom = %1%.",
df, Policy());
return df - 2;
}