55 lines
1.2 KiB
PHP
55 lines
1.2 KiB
PHP
<?php
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declare(strict_types=1);
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namespace Phpml\FeatureExtraction;
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use Phpml\Transformer;
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class TfIdfTransformer implements Transformer
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{
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/**
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* @var array
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*/
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private $idf = [];
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public function __construct(array $samples = [])
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{
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if (count($samples) > 0) {
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$this->fit($samples);
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}
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}
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public function fit(array $samples, ?array $targets = null): void
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{
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$this->countTokensFrequency($samples);
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$count = count($samples);
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foreach ($this->idf as &$value) {
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$value = log((float) ($count / $value), 10.0);
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}
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}
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public function transform(array &$samples, ?array &$targets = null): void
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{
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foreach ($samples as &$sample) {
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foreach ($sample as $index => &$feature) {
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$feature *= $this->idf[$index];
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}
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}
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}
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private function countTokensFrequency(array $samples): void
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{
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$this->idf = array_fill_keys(array_keys($samples[0]), 0);
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foreach ($samples as $sample) {
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foreach ($sample as $index => $count) {
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if ($count > 0) {
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++$this->idf[$index];
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}
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}
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}
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}
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}
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