Histogram.hpp

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#ifndef __NUMERIC_HISTOGRAM_HPP__
#define __NUMERIC_HISTOGRAM_HPP__

#include <algorithm>

namespace numeric
{

template <class T>
struct Buckets
{
    int count;
    double min_val, max_val;
    std::vector<T> buckets;

    Buckets( int count, double min_val, double max_val, const T& initial = T() )
        : count( count ), min_val( min_val ), max_val( max_val ), buckets( count, initial )
    {
        assert( count > 0 );
        assert( min_val < max_val );
    }

    const T& operator[]( size_t idx ) const
    {
        return buckets[idx];
    }

    T& operator[]( size_t idx )
    {
        return buckets[idx];
    }
    
    size_t getIndex( double value ) const
    {
        int idx = (value - min_val) / (max_val - min_val) * count;
        return std::min( count-1, std::max( 0, idx ) );
    }

    T& get( double value )
    {
        return buckets[ getIndex( value ) ];
    }

    double getBucketWidth() const
    {
        return (max_val - min_val)/count; 
    }

    double getUpperBound( size_t idx ) const
    {
        return min_val + ( (idx+1) * getBucketWidth() );
    }

    double getLowerBound( size_t idx ) const
    {
        return min_val + ( (idx) * getBucketWidth() );
    }

    double getCenter( size_t idx ) const
    {
        return min_val + ( (idx+0.5) * getBucketWidth() );
    }

    size_t size() const
    {
        return buckets.size();
    }
    
};

struct Histogram : public Buckets<size_t>
{
    size_t n;

    Histogram( int count, double min_val, double max_val )
        : Buckets<size_t>( count, min_val, max_val ), n(0)
    {
    }

    void update( double value )
    {
        ++n;
        ++get( value );
    }

    double getRelative( size_t idx ) const
    {
        return operator[]( idx ) / getBucketWidth() / (double)total();
    }

    size_t total() const
    {
        return n;
    }
};

}

#endif