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304 lines
8.7 KiB
304 lines
8.7 KiB
2 years ago
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<?php
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// This file is part of Moodle - http://moodle.org/
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//
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// Moodle is free software: you can redistribute it and/or modify
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// it under the terms of the GNU General Public License as published by
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// the Free Software Foundation, either version 3 of the License, or
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// (at your option) any later version.
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//
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// Moodle is distributed in the hope that it will be useful,
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// but WITHOUT ANY WARRANTY; without even the implied warranty of
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// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
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// GNU General Public License for more details.
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//
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// You should have received a copy of the GNU General Public License
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// along with Moodle. If not, see <http://www.gnu.org/licenses/>.
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/**
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* Question statistics calculations class. Used in the quiz statistics report but also available for use elsewhere.
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*
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* @package core
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* @subpackage questionbank
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* @copyright 2013 Open University
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* @author Jamie Pratt <me@jamiep.org>
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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namespace core_question\statistics\questions;
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defined('MOODLE_INTERNAL') || die();
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/**
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* This class is used to return the stats as calculated by {@link \core_question\statistics\questions\calculator}
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*
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* @copyright 2013 Open University
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* @author Jamie Pratt <me@jamiep.org>
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* @license http://www.gnu.org/copyleft/gpl.html GNU GPL v3 or later
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*/
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class calculated {
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public $questionid;
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// These first fields are the final fields cached in the db and shown in reports.
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// See : http://docs.moodle.org/dev/Quiz_statistics_calculations#Position_statistics .
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public $slot = null;
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/**
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* @var null|integer if this property is not null then this is the stats for a variant of a question or when inherited by
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* calculated_for_subquestion and not null then this is the stats for a variant of a sub question.
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*/
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public $variant = null;
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/**
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* @var bool is this a sub question.
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*/
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public $subquestion = false;
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/**
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* @var string if this stat has been picked as a min, median or maximum facility value then this string says which stat this
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* is. Prepended to question name for display.
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*/
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public $minmedianmaxnotice = '';
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/**
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* @var int total attempts at this question.
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*/
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public $s = 0;
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/**
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* @var float effective weight of this question.
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*/
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public $effectiveweight;
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/**
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* @var bool is covariance of this questions mark with other question marks negative?
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*/
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public $negcovar;
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/**
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* @var float
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*/
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public $discriminationindex;
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/**
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* @var float
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*/
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public $discriminativeefficiency;
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/**
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* @var float standard deviation
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*/
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public $sd;
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/**
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* @var float
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*/
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public $facility;
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/**
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* @var float max mark achievable for this question.
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*/
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public $maxmark;
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/**
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* @var string comma separated list of the positions in which this question appears.
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*/
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public $positions;
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/**
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* @var null|float The average score that students would have got by guessing randomly. Or null if not calculable.
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*/
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public $randomguessscore = null;
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// End of fields in db.
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protected $fieldsindb = array('questionid', 'slot', 'subquestion', 's', 'effectiveweight', 'negcovar', 'discriminationindex',
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'discriminativeefficiency', 'sd', 'facility', 'subquestions', 'maxmark', 'positions', 'randomguessscore', 'variant');
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// Fields used for intermediate calculations.
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public $totalmarks = 0;
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public $totalothermarks = 0;
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/**
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* @var float The total of marks achieved for all positions in all attempts where this item was seen.
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*/
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public $totalsummarks = 0;
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public $markvariancesum = 0;
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public $othermarkvariancesum = 0;
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public $covariancesum = 0;
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public $covariancemaxsum = 0;
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public $subquestions = '';
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public $covariancewithoverallmarksum = 0;
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public $markarray = array();
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public $othermarksarray = array();
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public $markaverage;
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public $othermarkaverage;
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/**
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* @var float The average for all attempts, of the sum of the marks for all positions in which this item appeared.
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*/
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public $summarksaverage;
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public $markvariance;
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public $othermarkvariance;
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public $covariance;
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public $covariancemax;
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public $covariancewithoverallmark;
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/**
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* @var object full question data
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*/
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public $question;
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/**
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* An array of calculated stats for each variant of the question. Even when there is just one variant we still calculate this
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* data as there is no way to know if there are variants before we have finished going through the attempt data one time.
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*
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* @var calculated[] $variants
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*/
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public $variantstats = array();
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/**
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* Set if this record has been retrieved from cache. This is the time that the statistics were calculated.
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*
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* @var integer
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*/
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public $timemodified;
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/**
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* Set up a calculated instance ready to store a question's (or a variant of a slot's question's)
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* stats for one slot in the quiz.
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*
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* @param null|object $question
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* @param null|int $slot
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* @param null|int $variant
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*/
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public function __construct($question = null, $slot = null, $variant = null) {
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if ($question !== null) {
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$this->questionid = $question->id;
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$this->maxmark = $question->maxmark;
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$this->positions = $question->number;
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$this->question = $question;
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}
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if ($slot !== null) {
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$this->slot = $slot;
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}
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if ($variant !== null) {
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$this->variant = $variant;
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}
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}
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/**
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* Used to determine which random questions pull sub questions from the same pools. Where pool means category and possibly
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* all the sub categories of that category.
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*
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* @return null|string represents the pool of questions from which this question draws if it is random, or null if not.
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*/
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public function random_selector_string() {
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if ($this->question->qtype == 'random') {
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return $this->question->category .'/'. $this->question->questiontext;
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} else {
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return null;
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}
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}
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/**
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* Cache calculated stats stored in this object in 'question_statistics' table.
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*
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* @param \qubaid_condition $qubaids
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*/
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public function cache($qubaids) {
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global $DB;
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$toinsert = new \stdClass();
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$toinsert->hashcode = $qubaids->get_hash_code();
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$toinsert->timemodified = time();
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foreach ($this->fieldsindb as $field) {
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$toinsert->{$field} = $this->{$field};
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}
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$DB->insert_record('question_statistics', $toinsert, false);
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if ($this->get_variants()) {
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foreach ($this->variantstats as $variantstat) {
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$variantstat->cache($qubaids);
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}
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}
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}
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/**
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* Load properties of this class from db record.
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*
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* @param object $record Given a record from 'question_statistics' copy stats from record to properties.
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*/
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public function populate_from_record($record) {
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foreach ($this->fieldsindb as $field) {
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$this->$field = $record->$field;
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}
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$this->timemodified = $record->timemodified;
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}
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/**
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* Sort the variants of this question by variant number.
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*/
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public function sort_variants() {
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ksort($this->variantstats);
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}
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/**
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* Get any sub question ids for this question.
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*
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* @return int[] array of sub-question ids or empty array if there are none.
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*/
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public function get_sub_question_ids() {
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if ($this->subquestions !== '') {
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return explode(',', $this->subquestions);
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} else {
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return array();
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}
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}
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/**
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* Array of variants that have appeared in the attempt data for this question. Or an empty array if there is only one variant.
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*
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* @return int[] the variant nos.
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*/
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public function get_variants() {
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$variants = array_keys($this->variantstats);
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if (count($variants) > 1 || reset($variants) != 1) {
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return $variants;
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} else {
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return array();
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}
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}
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/**
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* Do we break down the stats for this question by variant or not?
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*
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* @return bool Do we?
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*/
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public function break_down_by_variant() {
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$qtype = \question_bank::get_qtype($this->question->qtype);
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return $qtype->break_down_stats_and_response_analysis_by_variant($this->question);
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}
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/**
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* Delete the data structure for storing variant stats.
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*/
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public function clear_variants() {
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$this->variantstats = array();
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}
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}
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