histogramUniform.hpp

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/** \file histogramUniform.hpp
 * \author Jared R. Males
 * \brief  Header for the std::vector utilities
 * \ingroup gen_math_files
 *
 */
 
//***********************************************************************//
// Copyright 2015, 2016, 2017 Jared R. Males (jaredmales@gmail.com)
//
// This file is part of mxlib.
//
// mxlib is free software: you can redistribute it and/or modify
// it under the terms of the GNU General Public License as published by
// the Free Software Foundation, either version 3 of the License, or
// (at your option) any later version.
//
// mxlib is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
//
// You should have received a copy of the GNU General Public License
// along with mxlib.  If not, see <http://www.gnu.org/licenses/>.
//***********************************************************************//
 
#ifndef math_histogramUniform_hpp
#define math_histogramUniform_hpp
 
namespace mx
{
namespace math
{
 
/// A histogram with uniform bin spacing
/** Calculates the frequency in bins with uniform spacing.
 *
 * \tparam realT the real data type
 *
 * \ingroup gen_math
 */
template <typename realT>
class histogramUniform
{
  public:
    realT m_min{ 0 };   ///< The mininum bin location
    realT m_max{ 0 };   ///< The maximum bin location
    realT m_width{ 0 }; ///< The bin width
 
    std::vector<realT> _freqs; ///< The frequencies, one for each bin.
 
    /// Default c'tor, does not allocate.
    /** Must call setup before use */
    histogramUniform()
    {
    }
 
    /// Setup the histogram, performing allocations.
    histogramUniform( realT mn, ///< [in] the new minimum bin location
                      realT mx, ///< [in] the new maximum bin location
                      realT w   ///< [in] the bin width
                      )
        : m_min( mn ), m_max( mx ), m_width( w )
    {
        reset();
    }
 
    /// Setup the histogram, performing allocations.
    void setup( realT mn, ///< [in] the new minimum bin location
                realT mx, ///< [in] the new maximum bin location
                realT w   ///< [in] the bin width
    )
    {
        m_min = mn;
        m_max = mx;
        m_width = w;
 
        reset();
    }
 
    /// Resize and 0 the frequency vector.  Assumes m_min, m_max, and m_width are set.
    void reset()
    {
        _freqs.resize( ( m_max - m_min ) / m_width + 1, 0 );
    }
 
    /// Accumulate a value in the appropriate bin.
    void accum( const realT &val /**< [in] The value to accumulate */ )
    {
        int i = ( val - m_min ) / m_width;
        if( i < 0 )
            i = 0;
        if( i >= _freqs.size() )
            i = _freqs.size() - 1;
 
        ++_freqs[i];
    }
 
    /// Accumulate a vector of values.
    void accum( const std::vector<realT> &vals /**< [in] The vector of values to accumulate */ )
    {
        for( int i = 0; i < vals.size(); ++i )
            accum( vals[i] );
    }
 
    /// Get the frequency in the i-th bin.
    realT freq( int i /**< [in] the bin number */ )
    {
        return _freqs[i]; ///\returns the current value of _freqs[i].
    }
 
    /// Get the number of bins
    int bins()
    {
        return _freqs.size(); ///\returns the size of the frequency vector.
    }
 
    /// Get the value of the left-edge of the i-th bin.
    realT binLeft( int i /**< [in] the bin number */ )
    {
        return m_min + i * m_width; ///\returns the value of the left-edge of the i-th bin.
    }
 
    /// Get the value of the middle of the i-th bin.
    realT binMid( int i /**< [in] the bin number */ )
    {
        return m_min + i * m_width + 0.5 * m_width; ///\returns the value of the middle of the i-th bin.
    }
 
    /// Get the value of the right edge of the i-th bin.
    realT binRight( int i /**< [in] the bin number */ )
    {
        return m_min + i * m_width + 1.0 * m_width; ///\returns the value of the right edge of the i-th bin.
    }
 
    /// Normalize the current frequencies so that the integral over all bins is 1.
    /** This normalizes the histogram so that it is a probability distribution, such that the sum
     * \f$ \sum_i P_i \Delta x = 1 \f$ where \f$ \Delta x \f$ is the bin width.
     */
    void normalize(
        int excludeTop =
            0 /**< [in] [optional] specifies a number of bins at the top of the range to exclude from the sum */ )
    {
        realT sum = 0;
 
        for( int i = 0; i < _freqs.size() - excludeTop; ++i )
        {
            sum += _freqs[i];
        }
 
        for( int i = 0; i < _freqs.size(); ++i )
        {
            _freqs[i] /= ( sum * m_width );
        }
    }
};
 
} // namespace math
} // namespace mx
 
#endif // math_histogramUniform_hpp