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<?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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php-ai /
php-ml
