point_mean.h

// Description: Mean of a point-set
// Documentation: statistics.txt

#ifndef PASTELMATH_POINT_MEAN_H
#define PASTELMATH_POINT_MEAN_H

#include "pastel/sys/pointset/pointset_concept.h"
#include "pastel/sys/vector.h"

namespace Pastel
{

    //! Returns the mean of a point set.
    /*!
   Time complexity:
   O(nd)
   where
   n = size(pointSet), and
   d = pointSetDimension(pointSet).

   returns:
   [sum_{i = 1}^n x_i] / n
   */
    template <
        typename PointSet,
        Requires<
            Models<PointSet, PointSet_Concept>
        > = 0
    >
    auto pointMean(PointSet pointSet)
        -> Vector<PointSet_Real<PointSet>, Locator_N<PointSet_Locator<PointSet>>::value>
    {
        using Locator = PointSet_Locator<PointSet>;
        using Real = PointSet_Real<PointSet>;

        integer d = pointSetDimension(pointSet);
        ENSURE_OP(d, >=, 0);

        Vector<Real, Locator_N<Locator>::value> result(ofDimension(d), 0);

        if (emptySet(pointSet) || d == 0)
        {
            return result;
        }

        integer n = 0;
        RANGES_FOR(auto&& point, pointSet)
        {
            for (integer i = 0;i < d;++i)
            {
                result[i] += pointAxis(point, i);
            }
            ++n;
        }

        return result / n;
    }

}

#endif