Proyectos de Subversion Moodle

<?php

declare(strict_types=1);

namespace Phpml\Classification;

use Phpml\Helper\Predictable;

use Phpml\Helper\Trainable;

use Phpml\Math\Distance;

use Phpml\Math\Distance\Euclidean;

class KNearestNeighbors implements Classifier

{

    use Trainable;

    use Predictable;

    /**

     * @var int

     */

    private $k;

    /**

     * @var Distance

     */

    private $distanceMetric;

    /**

     * @param Distance|null $distanceMetric (if null then Euclidean distance as default)

     */

    public function __construct(int $k = 3, ?Distance $distanceMetric = null)

    {

        if ($distanceMetric === null) {

            $distanceMetric = new Euclidean();

        }

        $this->k = $k;

        $this->samples = [];

        $this->targets = [];

        $this->distanceMetric = $distanceMetric;

    }

    /**

     * @return mixed

     */

    protected function predictSample(array $sample)

    {

        $distances = $this->kNeighborsDistances($sample);

        $predictions = (array) array_combine(array_values($this->targets), array_fill(0, count($this->targets), 0));

        foreach (array_keys($distances) as $index) {

            ++$predictions[$this->targets[$index]];

        }

        arsort($predictions);

        reset($predictions);

        return key($predictions);

    }

    /**

     * @throws \Phpml\Exception\InvalidArgumentException

     */

    private function kNeighborsDistances(array $sample): array

    {

        $distances = [];

        foreach ($this->samples as $index => $neighbor) {

            $distances[$index] = $this->distanceMetric->distance($sample, $neighbor);

        }

        asort($distances);

        return array_slice($distances, 0, $this->k, true);

    }

}