question/classes/statistics/questions/calculated_random_question_summary.php

   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  * Question statistics calculations class. Used in the quiz statistics report.
  19  *
  20  * @package    core_question
  21  * @copyright  2018 Ryan Wyllie <ryan@moodle.com>
  22  * @license    http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  23  */
  24
  25 namespace core_question\statistics\questions;
  26 defined('MOODLE_INTERNAL') || die();
  27
  28 /**
  29  * Class calculated_random_question_summary
  30  *
  31  * This class is used to indicate the statistics for a random question slot should
  32  * be rendered with a link to a summary of the displayed questions.
  33  *
  34  * It's used in the limited view of the statistics calculation in lieu of adding
  35  * the stats for each subquestion individually.
  36  *
  37  * @copyright 2018 Ryan Wyllie <ryan@moodle.com>
  38  * @license   http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
  39  */
  40 class calculated_random_question_summary extends calculated {
  41
  42     /**
  43      * @var int only set immediately before display in the table. The order of display in the table.
  44      */
  45     public $subqdisplayorder;
  46
  47     /**
  48      * @var calculated[] The instances storing the calculated stats of the questions that are being summarised.
  49      */
  50     protected $subqstats;
  51
  52     /**
  53      * calculated_random_question_summary constructor.
  54      *
  55      * @param \stdClass $question
  56      * @param int $slot
  57      * @param calculated[] $subqstats The instances of the calculated stats of the questions that are being summarised.
  58      */
  59     public function __construct($question, $slot, $subqstats) {
  60         parent::__construct($question, $slot);
  61
  62         $this->subqstats = $subqstats;
  63         $this->subquestions = implode(',', array_column($subqstats, 'questionid'));
  64     }
  65
  66     /**
  67      * This is a summary stat so never breakdown by variant.
  68      *
  69      * @return bool
  70      */
  71     public function break_down_by_variant() {
  72         return false;
  73     }
  74
  75     /**
  76      * Returns the minimum and maximum values of the given attribute in the summarised calculated stats.
  77      *
  78      * @param string $attribute The attribute that we are looking for its extremums.
  79      * @return array An array of [min,max]
  80      */
  81     public function get_min_max_of($attribute) {
  82         $getmethod = 'get_min_max_of_' . $attribute;
  83         if (method_exists($this, $getmethod)) {
  84             return $this->$getmethod();
  85         } else {
  86             $min = $max = null;
  87
  88             // We cannot simply use min or max functions because, in theory, some attributes might be non-scalar.
  89             foreach (array_column($this->subqstats, $attribute) as $value) {
  90                 if (is_scalar($value)) {
  91                     if (!isset($min)) {
  92                         $min = $value;
  93                     }
  94                     if (!isset($max)) {
  95                         $max = $value;
  96                     }
  97
  98                     $min = min($min, $value);
  99                     $max = max($max, $value);
 100                 }
 101             }
 102
 103             return [$min, $max];
 104         }
 105     }
 106
 107     /**
 108      * Returns the minimum and maximum values of the standard deviation in the summarised calculated stats.
 109      * @return array An array of [min,max]
 110      */
 111     protected function get_min_max_of_sd() {
 112         $min = $max = null;
 113
 114         foreach ($this->subqstats as $subqstat) {
 115             if (isset($subqstat->sd) && $subqstat->maxmark) {
 116                 if (!isset($min)) {
 117                     $min = $subqstat->sd / $subqstat->maxmark;
 118                 }
 119                 if (!isset($max)) {
 120                     $max = $subqstat->sd / $subqstat->maxmark;
 121                 }
 122
 123                 $min = min($min, $subqstat->sd / $subqstat->maxmark);
 124                 $max = max($max, $subqstat->sd / $subqstat->maxmark);
 125             }
 126         }
 127
 128         return [$min, $max];
 129     }
 130 }