source: trunk/lib/classifier/CrossSplitting.cc @ 460

// $Id: CrossSplitting.cc 460 2005-12-16 12:40:06Z peter $


#include <c++_tools/gslapi/vector.h>
#include <c++_tools/classifier/CrossSplitting.h>
#include <c++_tools/random/random.h>

#include <vector>

namespace theplu {
namespace classifier {  

  CrossSplitting::CrossSplitting(const theplu::gslapi::vector& target, 
                                   const size_t k)
    :count_(0),index_negative_(std::vector<size_t>()),
     index_positive_(std::vector<size_t>()), k_(k)
 
  { 
    for (size_t i=0; i<target.size(); i++){
      if (target(i)==1)
        index_positive_.push_back(i);
      else
        index_negative_.push_back(i);
    }

    random::DiscreteUniform a;
    random_shuffle(index_negative_.begin(), index_negative_.end(), a);
    random_shuffle(index_positive_.begin(), index_positive_.end(), a);
  }

  std::vector<size_t> CrossSplitting::next()
  {
    random::DiscreteUniform a;
    if (count_==k_){
      count_=0;
      random_shuffle(index_negative_.begin(), index_negative_.end(), a);
      random_shuffle(index_positive_.begin(), index_positive_.end(), a);
    }
      
    count_++;
    std::vector<size_t> training_set;

    size_t begin = int(index_positive_.size()*(count_-1)/k_);
    size_t end = int(index_positive_.size()*count_/k_);
    for (size_t i=0; i<index_positive_.size(); i++)
      if (i<begin || i>=end)
        training_set.push_back(index_positive_[i]);
    
    begin = int(index_negative_.size()*(count_-1)/k_);
    end = int(index_negative_.size()*count_/k_);
    for (size_t i=0; i<index_negative_.size(); i++)
      if (i<begin || i>=end)
        training_set.push_back(index_negative_[i]);
    
    return training_set ;
    
  }
  
}} // of namespace classifier and namespace theplu