Src/DasherCore/GameStatistics.h

   1 #ifndef __GameStatistics_h__
   2 #define __GameStatistics_h__
   3
   4 // Code examples modified from C++ Cookbook O'Reilly.
   5 // Code use falls under fair use as dicussed in the book
   6
   7 #include <numeric>
   8 #include <cmath>
   9 #include <algorithm>
  10 #include <functional>
  11 #include <vector>
  12
  13 template<class T>
  14 T nthPower(T x, int n)
  15 {
  16   T ret = x;
  17   for (int i=1; i < n; ++i)
  18     ret*=x;
  19   return ret;
  20 }
  21
  22 template<class T>
  23 struct SumDiffNthPower
  24 {
  25   SumDiffNthPower(T x, int n) : m_mean(x), m_n(n) {}
  26   T operator()(T sum, T current)
  27   {
  28     return sum+nthPower(current-m_mean, m_n);
  29   }
  30   T m_mean;
  31   int m_n;
  32 };
  33
  34 template<class T, class Iter_T>
  35   T nthMoment(int n, Iter_T first, Iter_T last, T mean)
  36 {
  37   size_t cnt = last - first;
  38   return std::accumulate(first, last, T(), SumDiffNthPower<T>(mean, n))/cnt;
  39 }
  40 template<typename T>
  41 std::string ComputeStats(const std::vector<T> &v)
  42 {
  43   if (v.empty()) return "";
  44
  45   double m1 = nthMoment(1,v.begin(), v.end(), 0.0);
  46   double m2 = nthMoment(2,v.begin(), v.end(), m1);
  47   double m3 = nthMoment(3,v.begin(), v.end(), m1);
  48   double m4 = nthMoment(4,v.begin(), v.end(), m1);
  49
  50   double dev = sqrt(m2); // Standard Deviation
  51   double skew = m3/(m2*dev); // Skewness
  52   double kurt = m4 / (m2*m2) - 3.0; // Excess Kurtosis
  53
  54   ostringstream m_Statsbreakdown("");
  55 #define SEP " "
  56   m_Statsbreakdown << "Samples: " << v.size() << SEP
  57     << "Mean: " << m1 << SEP
  58     << "StdDev: " << dev << SEP
  59     << "Skew: " << skew << SEP
  60     << "Kurt: " << kurt << SEP;
  61 #undef SEP
  62   return m_Statsbreakdown.str();
  63 }
  64
  65 template<class A, class B, class T>
  66 struct MemberSumDiffNthPower
  67 {
  68   MemberSumDiffNthPower(A T::* pm, B x, int n) : m_mean(x), m_pm(pm), m_n(n) {}
  69   B operator()(B sum, T current)
  70   {
  71     return sum+nthPower(current.*m_pm-m_mean, m_n);
  72   }
  73   B m_mean;
  74   A T::* m_pm;
  75   int m_n;
  76 };
  77
  78 template<class T, class Iter_T, class A, class B>
  79   B MemberNthMoment(int n, Iter_T first, Iter_T last, A T::* pmember, B mean)
  80 {
  81   size_t cnt = last - first;
  82   return std::accumulate(first, last, B(), MemberSumDiffNthPower<A,B,T>(pmember,mean,n))/cnt;
  83 }
  84
  85 #endif