67 lines
1.8 KiB
PHP
67 lines
1.8 KiB
PHP
<?php
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declare(strict_types=1);
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namespace Phpml\Preprocessing;
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use Phpml\Exception\InvalidArgumentException;
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final class OneHotEncoder implements Preprocessor
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{
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/**
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* @var bool
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*/
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private $ignoreUnknown;
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/**
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* @var array
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*/
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private $categories = [];
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public function __construct(bool $ignoreUnknown = false)
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{
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$this->ignoreUnknown = $ignoreUnknown;
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}
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public function fit(array $samples, ?array $targets = null): void
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{
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foreach (array_keys(array_values(current($samples))) as $column) {
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$this->fitColumn($column, array_values(array_unique(array_column($samples, $column))));
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}
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}
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public function transform(array &$samples, ?array &$targets = null): void
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{
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foreach ($samples as &$sample) {
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$sample = $this->transformSample(array_values($sample));
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}
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}
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private function fitColumn(int $column, array $values): void
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{
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$count = count($values);
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foreach ($values as $index => $value) {
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$map = array_fill(0, $count, 0);
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$map[$index] = 1;
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$this->categories[$column][$value] = $map;
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}
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}
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private function transformSample(array $sample): array
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{
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$encoded = [];
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foreach ($sample as $column => $feature) {
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if (!isset($this->categories[$column][$feature]) && !$this->ignoreUnknown) {
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throw new InvalidArgumentException(sprintf('Missing category "%s" for column %s in trained encoder', $feature, $column));
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}
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$encoded = array_merge(
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$encoded,
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$this->categories[$column][$feature] ?? array_fill(0, count($this->categories[$column]), 0)
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);
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}
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return $encoded;
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}
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}
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