76 lines
1.7 KiB
PHP
76 lines
1.7 KiB
PHP
<?php
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declare(strict_types=1);
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namespace Phpml\Classification;
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use Phpml\Helper\Predictable;
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use Phpml\Helper\Trainable;
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use Phpml\Math\Distance;
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use Phpml\Math\Distance\Euclidean;
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class KNearestNeighbors implements Classifier
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{
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use Trainable;
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use Predictable;
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/**
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* @var int
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*/
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private $k;
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/**
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* @var Distance
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*/
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private $distanceMetric;
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/**
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* @param Distance|null $distanceMetric (if null then Euclidean distance as default)
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*/
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public function __construct(int $k = 3, ?Distance $distanceMetric = null)
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{
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if ($distanceMetric === null) {
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$distanceMetric = new Euclidean();
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}
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$this->k = $k;
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$this->samples = [];
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$this->targets = [];
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$this->distanceMetric = $distanceMetric;
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}
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/**
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* @return mixed
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*/
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protected function predictSample(array $sample)
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{
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$distances = $this->kNeighborsDistances($sample);
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$predictions = (array) array_combine(array_values($this->targets), array_fill(0, count($this->targets), 0));
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foreach (array_keys($distances) as $index) {
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++$predictions[$this->targets[$index]];
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}
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arsort($predictions);
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reset($predictions);
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return key($predictions);
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}
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/**
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* @throws \Phpml\Exception\InvalidArgumentException
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*/
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private function kNeighborsDistances(array $sample): array
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{
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$distances = [];
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foreach ($this->samples as $index => $neighbor) {
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$distances[$index] = $this->distanceMetric->distance($sample, $neighbor);
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}
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asort($distances);
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return array_slice($distances, 0, $this->k, true);
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}
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}
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