1 ///////////////////////////////////////////////////////////////////////////////
2 // weighted_moment.hpp
3 //
4 //  Copyright 2006, Eric Niebler, Olivier Gygi. Distributed under the Boost
5 //  Software License, Version 1.0. (See accompanying file
6 //  LICENSE_1_0.txt or copy at http://www.boost.org/LICENSE_1_0.txt)
7 
8 #ifndef BOOST_ACCUMULATORS_STATISTICS_WEIGHTED_MOMENT_HPP_EAN_15_11_2005
9 #define BOOST_ACCUMULATORS_STATISTICS_WEIGHTED_MOMENT_HPP_EAN_15_11_2005
10 
11 #include <boost/config/no_tr1/cmath.hpp>
12 #include <boost/mpl/int.hpp>
13 #include <boost/mpl/assert.hpp>
14 #include <boost/mpl/placeholders.hpp>
15 #include <boost/preprocessor/arithmetic/inc.hpp>
16 #include <boost/preprocessor/repetition/repeat_from_to.hpp>
17 #include <boost/preprocessor/repetition/enum_trailing_params.hpp>
18 #include <boost/preprocessor/repetition/enum_trailing_binary_params.hpp>
19 #include <boost/accumulators/framework/accumulator_base.hpp>
20 #include <boost/accumulators/framework/extractor.hpp>
21 #include <boost/accumulators/numeric/functional.hpp>
22 #include <boost/accumulators/framework/parameters/sample.hpp>
23 #include <boost/accumulators/framework/depends_on.hpp>
24 #include <boost/accumulators/statistics_fwd.hpp>
25 #include <boost/accumulators/statistics/count.hpp>
26 #include <boost/accumulators/statistics/moment.hpp> // for pow()
27 #include <boost/accumulators/statistics/sum.hpp>
28 
29 namespace boost { namespace accumulators
30 {
31 
32 namespace impl
33 {
34     ///////////////////////////////////////////////////////////////////////////////
35     // weighted_moment_impl
36     template<typename N, typename Sample, typename Weight>
37     struct weighted_moment_impl
38       : accumulator_base // TODO: also depends_on sum of powers
39     {
40         BOOST_MPL_ASSERT_RELATION(N::value, >, 0);
41         typedef typename numeric::functional::multiplies<Sample, Weight>::result_type weighted_sample;
42         // for boost::result_of
43         typedef typename numeric::functional::fdiv<weighted_sample, Weight>::result_type result_type;
44 
45         template<typename Args>
weighted_moment_implboost::accumulators::impl::weighted_moment_impl46         weighted_moment_impl(Args const &args)
47           : sum(args[sample | Sample()] * numeric::one<Weight>::value)
48         {
49         }
50 
51         template<typename Args>
operator ()boost::accumulators::impl::weighted_moment_impl52         void operator ()(Args const &args)
53         {
54             this->sum += args[weight] * numeric::pow(args[sample], N());
55         }
56 
57         template<typename Args>
resultboost::accumulators::impl::weighted_moment_impl58         result_type result(Args const &args) const
59         {
60             return numeric::fdiv(this->sum, sum_of_weights(args));
61         }
62 
63         // make this accumulator serializeable
64         template<class Archive>
serializeboost::accumulators::impl::weighted_moment_impl65         void serialize(Archive & ar, const unsigned int file_version)
66         {
67             ar & sum;
68         }
69 
70     private:
71         weighted_sample sum;
72     };
73 
74 } // namespace impl
75 
76 ///////////////////////////////////////////////////////////////////////////////
77 // tag::weighted_moment
78 //
79 namespace tag
80 {
81     template<int N>
82     struct weighted_moment
83       : depends_on<count, sum_of_weights>
84     {
85         /// INTERNAL ONLY
86         ///
87         typedef accumulators::impl::weighted_moment_impl<mpl::int_<N>, mpl::_1, mpl::_2> impl;
88     };
89 }
90 
91 ///////////////////////////////////////////////////////////////////////////////
92 // extract::weighted_moment
93 //
94 namespace extract
95 {
96     BOOST_ACCUMULATORS_DEFINE_EXTRACTOR(tag, weighted_moment, (int))
97 }
98 
99 using extract::weighted_moment;
100 
101 }} // namespace boost::accumulators
102 
103 #endif
104