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   1  <?php
   2  // This file is part of Moodle - http://moodle.org/
   3  //
   4  // Moodle is free software: you can redistribute it and/or modify
   5  // it under the terms of the GNU General Public License as published by
   6  // the Free Software Foundation, either version 3 of the License, or
   7  // (at your option) any later version.
   8  //
   9  // Moodle is distributed in the hope that it will be useful,
  10  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  11  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  12  // GNU General Public License for more details.
  13  //
  14  // You should have received a copy of the GNU General Public License
  15  // along with Moodle.  If not, see <http://www.gnu.org/licenses/>.
  16  
  17  /**
  18   * Linear values target.
  19   *
  20   * @package   core_analytics
  21   * @copyright 2017 David Monllao {@link http://www.davidmonllao.com}
  22   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23   */
  24  
  25  namespace core_analytics\local\target;
  26  
  27  defined('MOODLE_INTERNAL') || die();
  28  
  29  /**
  30   * Linear values target.
  31   *
  32   * @package   core_analytics
  33   * @copyright 2017 David Monllao {@link http://www.davidmonllao.com}
  34   * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  35   */
  36  abstract class linear extends base {
  37  
  38      /**
  39       * Are the calculated values this target returns linear values?
  40       *
  41       * @return bool
  42       */
  43      public function is_linear() {
  44          // Not supported yet.
  45          throw new \coding_exception('Sorry, this version\'s prediction processors only support targets with binary values.' .
  46              ' You can write your own and overwrite this method though.');
  47      }
  48  
  49      /**
  50       * How positive is this calculated value?
  51       *
  52       * @param float $value
  53       * @param string $ignoredsubtype
  54       * @return int
  55       */
  56      public function get_calculation_outcome($value, $ignoredsubtype = false) {
  57  
  58          // This is very generic, targets will probably be interested in overwriting this.
  59          $diff = static::get_max_value() - static::get_min_value();
  60          if (($value - static::get_min_value()) / $diff >= 0.5) {
  61              return self::OUTCOME_VERY_POSITIVE;
  62          }
  63          return self::OUTCOME_VERY_NEGATIVE;
  64      }
  65  
  66      /**
  67       * Gets the maximum value for this target
  68       *
  69       * @return float
  70       */
  71      public static function get_max_value() {
  72          // Coding exception as this will only be called if this target have linear values.
  73          throw new \coding_exception('Overwrite get_max_value() and return the target max value');
  74      }
  75  
  76      /**
  77       * Gets the minimum value for this target
  78       *
  79       * @return float
  80       */
  81      public static function get_min_value() {
  82          // Coding exception as this will only be called if this target have linear values.
  83          throw new \coding_exception('Overwrite get_min_value() and return the target min value');
  84      }
  85  
  86      /**
  87       * This method determines if a prediction is interesing for the model or not.
  88       *
  89       * @param mixed $predictedvalue
  90       * @param float $predictionscore
  91       * @return bool
  92       */
  93      public function triggers_callback($predictedvalue, $predictionscore) {
  94  
  95          if (!parent::triggers_callback($predictedvalue, $predictionscore)) {
  96              return false;
  97          }
  98  
  99          // People may not want to set a boundary.
 100          $boundary = $this->get_callback_boundary();
 101          if (!empty($boundary) && floatval($predictedvalue) < $boundary) {
 102              return false;
 103          }
 104  
 105          return true;
 106      }
 107  
 108      /**
 109       * Returns the minimum value that triggers the callback.
 110       *
 111       * @return float
 112       */
 113      protected function get_callback_boundary() {
 114          // Coding exception as this will only be called if this target have linear values.
 115          throw new \coding_exception('Overwrite get_callback_boundary() and return the min value that ' .
 116              'should trigger the callback');
 117      }
 118  }