IT++ Logo
exit.cpp
Go to the documentation of this file.
1 
29 #include <itpp/comm/exit.h>
30 #include <itpp/stat/histogram.h> //histogram class for mutual information computation
31 #include <itpp/base/itcompat.h>
32 
33 namespace itpp
34 {
35 double EXIT::Gaussian_Fct::operator()(double x) const
36 {
37  return (1.0/std::sqrt(_sigma*itpp::m_2pi))*std::exp(-itpp::sqr(x-(_sigma/2.0))/(2.0*_sigma))*::log2(1+std::exp(-x));
38 }
39 
40 double EXIT::extrinsic_mutual_info(const itpp::vec &obs, const itpp::bvec &cond, const int &N)
41 {
42  //initialize histogram
43  itpp::Histogram<double> hist(itpp::min(obs), itpp::max(obs), N);//common definition interval for both PDFs
44 
45  //conditional PDF knowing that a bit of 0 was emitted
46  itpp::ivec idx = itpp::find(cond==itpp::bin(0));
47  itpp::vec cond_obs = obs(idx);
48  hist.reset();//start counting
49  hist.update(cond_obs);
50  itpp::vec left_pdf = hist.get_pdf();//the pdf is computed without taking into account the interval length (step)
51  itpp::ivec left_int = itpp::find(left_pdf!=0);//integration interval for the left PDF
52 
53  //conditional PDF knowing that a bit of 1 was emitted
54  idx = itpp::find(cond==itpp::bin(1));
55  cond_obs = obs(idx);
56  hist.reset();//restart counting
57  hist.update(cond_obs);
58  itpp::vec right_pdf = hist.get_pdf();
59  itpp::ivec right_int = itpp::find(right_pdf!=0);//integration interval for the right PDF
60 
61  //mutual extrinsic information
62  itpp::vec left_half = itpp::elem_mult(left_pdf(left_int), itpp::log2(itpp::elem_div(2.0*left_pdf(left_int), left_pdf(left_int)+right_pdf(left_int))));
63  double IE = itpp::sum(left_half)-0.5*(left_half(0)+left_half(left_half.length()-1));//numerical integration without taking into account the inteval length (see conditional PDF computation)
64  itpp::vec right_half = itpp::elem_mult(right_pdf(right_int), itpp::log2(itpp::elem_div(2.0*right_pdf(right_int), left_pdf(right_int)+right_pdf(right_int))));
65  IE += itpp::sum(right_half)-0.5*(right_half(0)+right_half(right_half.length()-1));//numerical integration
66  IE *= 0.5;
67 
68  return IE;
69 }
70 
71 }//namespace itpp
72 
Mat< Num_T > elem_div(const Mat< Num_T > &m1, const Mat< Num_T > &m2)
Element wise division of two matrices.
Definition: mat.h:1688
const double m_2pi
Constant 2*Pi.
Definition: misc.h:106
Histogram computation class.
Definition: histogram.h:75
ivec find(const bvec &invector)
Return a integer vector with indicies where bvec == 1.
Definition: specmat.cpp:40
Mat< Num_T > elem_mult(const Mat< Num_T > &m1, const Mat< Num_T > &m2)
Element wise multiplication of two matrices.
Definition: mat.h:1582
void update(Num_T value)
Histogram update.
Definition: histogram.h:164
T sum(const Vec< T > &v)
Sum of all elements in the vector.
Definition: matfunc.h:59
T min(const Vec< T > &in)
Minimum value of vector.
Definition: min_max.h:125
vec exp(const vec &x)
Exp of the elements of a vector x.
Definition: log_exp.h:155
vec log2(const vec &x)
log-2 of the elements
Definition: log_exp.cpp:36
T max(const Vec< T > &v)
Maximum value of vector.
Definition: min_max.h:45
double extrinsic_mutual_info(const itpp::vec &obs, const itpp::bvec &cond, const int &N=100)
Computes the extrinsic mutual information.
Definition: exit.cpp:40
Definitions for EXtrinsic Information Transfer (EXIT) chart class.
itpp namespace
Definition: itmex.h:36
IT++ compatibility types and functions.
vec sqr(const cvec &data)
Absolute square of elements.
Definition: elem_math.cpp:36
Binary arithmetic (boolean) class.
Definition: binary.h:56
vec get_pdf() const
Experimental Probability Density Function (PDF) computation.
Definition: histogram.h:201
vec sqrt(const vec &x)
Square root of the elements.
Definition: elem_math.h:123
Histogram class - header file.
void reset()
Bins reset, so accumulation can be restarted.
Definition: histogram.h:95
SourceForge Logo

Generated on Sun Apr 10 2022 12:00:00 for IT++ by Doxygen 1.8.14