Proyectos de Subversion Moodle

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1 efrain 1 
<?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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}