/* statistics/trmean_source.c

 * 

 * Copyright (C) 2018 Patrick Alken

 * 

 * This program 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.

 * 

 * This program 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 this program; if not, write to the Free Software

 * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA 02110-1301, USA.

 */

double

FUNCTION (gsl_stats, trmean_from_sorted_data) (const double trim, const BASE sorted_data[],

                                               const size_t stride, const size_t size)

{

  if (trim >= 0.5)

    {

      return FUNCTION(gsl_stats, median_from_sorted_data)(sorted_data, stride, size);

    }

  else

    {

      size_t ilow = (size_t) floor(trim * size);

      size_t ihigh = size - ilow - 1;

      double mean = 0.0;

      double k = 0.0;

      size_t i;

      /* compute mean of middle samples in [ilow,ihigh] */

      for (i = ilow; i <= ihigh; ++i)

        {

          double delta = sorted_data[i * stride] - mean;

          k += 1.0;

          mean += delta / k;

        }

      return mean;

    }

}