metrics.h

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#if !defined(ULTRA_SRC_CALCULATE_METRICS_H)
#define      ULTRA_SRC_CALCULATE_METRICS_H
 
#include "kernel/gp/src/predictor.h"
 
#include <cmath>
#include <limits>
#include <ranges>
 
namespace ultra::src::metrics
{

template<ClassificationPredictor P>
[[nodiscard]] double accuracy(const P &p, const dataframe &d)
{
  Expects(d.classes() >= 2);
  Expects(d.size());
 
  const auto ok(std::ranges::count_if(
                  d,
                  [&p](const auto &e)
                  {
                    return p.tag(e.input).label == label(e);
                  }));
 
  return static_cast<double>(ok) / static_cast<double>(d.size());
}

template<RegressionPredictor P>
[[nodiscard]] double mae(const P &p, const dataframe &d)
{
  Expects(!d.classes());
  Expects(d.size());
 
  double sum(0.0);
  std::size_t n(0);
 
  for (const auto &e : d)
    if (const auto res(p(e.input)); has_value(res))
    {
      sum += std::fabs(std::get<D_DOUBLE>(res) - label_as<D_DOUBLE>(e));
      ++n;
    }
 
  return n ? sum / static_cast<double>(n)
           : std::numeric_limits<double>::infinity();
}
 
}  // namespace ultra::src::metrics
 
#endif  // include guard