confusion_matrix.h

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#ifndef META_CONFUSION_MATRIX_H_
#define META_CONFUSION_MATRIX_H_

#include <set>
#include "index/forward_index.h"
#include "meta.h"

namespace meta
{
namespace classify
{

class confusion_matrix
{
  public:
    confusion_matrix();

    void add(const class_label& predicted, const class_label& actual,
             size_t times = 1);

    void print_stats(std::ostream& out = std::cout) const;

    void print(std::ostream& out = std::cout) const;

    void print_result_pairs(std::ostream& out = std::cout) const;

    static size_t
        string_pair_hash(const std::pair<std::string, std::string>& strPair);

    // note: the following *cannot* be converted to a using declaration
    // without causing in internal compiler error (segmentation fault) in
    // GCC 4.8.2
    typedef std::unordered_map<std::pair<class_label, class_label>, size_t,
                               decltype(&confusion_matrix::string_pair_hash)>
        prediction_counts;

    const prediction_counts& predictions() const;

    double accuracy() const;

    confusion_matrix operator+(const confusion_matrix& other) const;

    confusion_matrix& operator+=(const confusion_matrix& other);

    static bool mcnemar_significant(const confusion_matrix& a,
                                    const confusion_matrix& b);

  private:
    void print_class_stats(std::ostream& out, const class_label& label,
                           double& prec, double& rec, double& f1,
                           size_t width) const;

    prediction_counts predictions_;

    std::set<class_label> classes_;

    std::unordered_map<class_label, size_t> counts_;

    size_t total_;
};
}
}

#endif