CHistogram.cpp

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/* +------------------------------------------------------------------------+
   |                     Mobile Robot Programming Toolkit (MRPT)            |
   |                          https://www.mrpt.org/                         |
   |                                                                        |
   | Copyright (c) 2005-2020, Individual contributors, see AUTHORS file     |
   | See: https://www.mrpt.org/Authors - All rights reserved.               |
   | Released under BSD License. See: https://www.mrpt.org/License          |
   +------------------------------------------------------------------------+ */

#include "math-precomp.h"  // Precompiled headers

#include <mrpt/core/exceptions.h>
#include <mrpt/math/CHistogram.h>
#include <mrpt/math/utils.h>  // linspace()

using namespace mrpt;
using namespace mrpt::math;

/*---------------------------------------------------------------
                    Constructor
 ---------------------------------------------------------------*/
CHistogram::CHistogram(const double min, const double max, const size_t nBins)
    : m_min(min), m_max(max), m_bins(nBins, 0), m_count(0)
{
    ASSERT_(nBins > 0);
    ASSERT_(max > min);
    m_binSizeInv = nBins / (m_max - m_min);
}

/*---------------------------------------------------------------
                        clear
 ---------------------------------------------------------------*/
void CHistogram::clear()
{
    m_bins.assign(m_bins.size(), 0);
    m_count = 0;
}

/*---------------------------------------------------------------
                            add
 ---------------------------------------------------------------*/
void CHistogram::add(const double x)
{
    ASSERT_(!m_bins.empty());
    if (x < m_min || x > m_max) return;

    auto ind = static_cast<size_t>(m_binSizeInv * (x - m_min));
    if (ind >= m_bins.size()) ind = m_bins.size() - 1;

    m_bins[ind]++;
    m_count++;
}

/*---------------------------------------------------------------
                    getBinCount
 ---------------------------------------------------------------*/
size_t CHistogram::getBinCount(const size_t index) const
{
    if (index >= m_bins.size()) THROW_EXCEPTION("Index out of bounds");

    return m_bins[index];
}

/*---------------------------------------------------------------
                    getBinRatio
 ---------------------------------------------------------------*/
double CHistogram::getBinRatio(const size_t index) const
{
    if (index >= m_bins.size()) THROW_EXCEPTION("Index out of bounds");

    if (m_count)
        return m_bins[index] / double(m_count);
    else
        return 0;
}

void CHistogram::getHistogram(
    std::vector<double>& x, std::vector<double>& hits) const
{
    linspace(m_min, m_max, m_bins.size(), x);
    const size_t N = m_bins.size();
    hits.resize(N);
    for (size_t i = 0; i < N; i++) hits[i] = static_cast<double>(m_bins[i]);
}

void CHistogram::getHistogramNormalized(
    std::vector<double>& x, std::vector<double>& hits) const
{
    const size_t N = m_bins.size();
    linspace(m_min, m_max, N, x);

    hits.resize(N);
    const double K = m_binSizeInv / m_count;
    for (size_t i = 0; i < N; i++) hits[i] = K * m_bins[i];
}

CHistogram CHistogram::createWithFixedWidth(
    double min, double max, double binWidth)
{
    ASSERT_(max > min);
    ASSERT_(binWidth > 0);
    return CHistogram(
        min, max, static_cast<size_t>(ceil((max - min) / binWidth)));
}