HistogramAverage.php

<?php
/**
 * Copyright (C) 2020 Graham Breach
 *
 * This program is free software: you can redistribute it and/or modify
 * it under the terms of the GNU Lesser 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 Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */
/**
 * For more information, please contact <graham@goat1000.com>
 */

namespace Goat1000\SVGGraph;

/**
 * Class for making averages work on Histograms
 */
class HistogramAverage extends Average {

  /**
   * Calculates the mean average for a dataset
   */
  protected function calculate(&$values, $dataset)
  {
    $sum = 0;
    $count = 0;
    foreach($values[$dataset] as $p) {
      if($p->value === null)
        continue;
      $sum += $p->value;
      ++$count;
    }

    // histogram data ends with a 0 to pad the axis out
    --$count;

    return $count > 0 ? $sum / $count : null;
  }
}