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106 lines
2.9 KiB
106 lines
2.9 KiB
<?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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* Binary classifier target.
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*
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* @package core_analytics
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* @copyright 2017 David Monllao {@link http://www.davidmonllao.com}
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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_analytics\local\target;
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defined('MOODLE_INTERNAL') || die();
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/**
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* Binary classifier target.
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*
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* @package core_analytics
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* @copyright 2017 David Monllao {@link http://www.davidmonllao.com}
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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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abstract class binary extends discrete {
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/**
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* is_linear
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*
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* @return bool
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*/
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public function is_linear() {
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return false;
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}
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/**
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* Returns the target discrete values.
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*
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* Only useful for targets using discrete values, must be overwriten if it is the case.
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*
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* @return array
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*/
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public static final function get_classes() {
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return array(0, 1);
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}
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/**
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* Returns the predicted classes that will be ignored.
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*
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* @return array
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*/
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public function ignored_predicted_classes() {
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// Zero-value class is usually ignored in binary classifiers.
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return array(0);
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}
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/**
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* Is the calculated value a positive outcome of this target?
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*
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* @param string $value
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* @param string $ignoredsubtype
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* @return int
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*/
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public function get_calculation_outcome($value, $ignoredsubtype = false) {
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if (!self::is_a_class($value)) {
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throw new \moodle_exception('errorpredictionformat', 'analytics');
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}
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if (in_array($value, $this->ignored_predicted_classes(), false)) {
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// Just in case, if it is ignored the prediction should not even be recorded but if it would, it is ignored now,
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// which should mean that is it nothing serious.
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return self::OUTCOME_VERY_POSITIVE;
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}
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// By default binaries are danger when prediction = 1.
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if ($value) {
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return self::OUTCOME_VERY_NEGATIVE;
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}
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return self::OUTCOME_VERY_POSITIVE;
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}
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/**
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* classes_description
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*
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* @return string[]
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*/
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protected static function classes_description() {
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return array(
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get_string('yes'),
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get_string('no')
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);
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}
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}
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