/**
* Load cached statistics from the database.
*
* @param $qubaids \qubaid_condition
* @return calculated The statistics for overall attempt scores or false if not cached.
*/
public function get_cached($qubaids)
{
global $DB;
$timemodified = time() - self::TIME_TO_CACHE;
$fromdb = $DB->get_record_select('quiz_statistics', 'hashcode = ? AND timemodified > ?', array($qubaids->get_hash_code(), $timemodified));
$stats = new calculated();
$stats->populate_from_record($fromdb);
return $stats;
}
/**
* Then loop through all questions for the first time.
*
* Perform some computations on the per-question statistics calculations after
* we have been through all the step data.
*
* @param calculated $stats question stats to update.
*/
protected function initial_question_walker($stats)
{
$stats->markaverage = $stats->totalmarks / $stats->s;
if ($stats->maxmark != 0) {
$stats->facility = $stats->markaverage / $stats->maxmark;
} else {
$stats->facility = null;
}
$stats->othermarkaverage = $stats->totalothermarks / $stats->s;
$stats->summarksaverage = $stats->totalsummarks / $stats->s;
sort($stats->markarray, SORT_NUMERIC);
sort($stats->othermarksarray, SORT_NUMERIC);
// Here we have collected enough data to make the decision about which questions have variants whose stats we also want to
// calculate. We delete the initialised structures where they are not needed.
if (!$stats->get_variants() || !$stats->break_down_by_variant()) {
$stats->clear_variants();
}
foreach ($stats->get_variants() as $variant) {
$this->initial_question_walker($stats->variantstats[$variant]);
}
}
