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<?php declare(strict_types=1); namespace Phpml\Preprocessing; use Phpml\Exception\NormalizerException; use Phpml\Math\Statistic\Mean; use Phpml\Math\Statistic\StandardDeviation; class Normalizer implements Preprocessor { public const NORM_L1 = 1; public const NORM_L2 = 2; public const NORM_STD = 3; /** * @var int */ private $norm; /** * @var bool */ private $fitted = false; /** * @var array */ private $std = []; /** * @var array */ private $mean = []; /** * @throws NormalizerException */ public function __construct(int $norm = self::NORM_L2) { if (!in_array($norm, [self::NORM_L1, self::NORM_L2, self::NORM_STD], true)) { throw new NormalizerException('Unknown norm supplied.'); } $this->norm = $norm; } public function fit(array $samples, ?array $targets = null): void { if ($this->fitted) { return; } if ($this->norm === self::NORM_STD) { $features = range(0, count($samples[0]) - 1); foreach ($features as $i) { $values = array_column($samples, $i); $this->std[$i] = StandardDeviation::population($values); $this->mean[$i] = Mean::arithmetic($values); } } $this->fitted = true; }< public function transform(array &$samples): void> public function transform(array &$samples, ?array &$targets = null): void{ $methods = [ self::NORM_L1 => 'normalizeL1', self::NORM_L2 => 'normalizeL2', self::NORM_STD => 'normalizeSTD', ]; $method = $methods[$this->norm]; $this->fit($samples); foreach ($samples as &$sample) { $this->{$method}($sample); } } private function normalizeL1(array &$sample): void { $norm1 = 0; foreach ($sample as $feature) { $norm1 += abs($feature); } if ($norm1 == 0) { $count = count($sample); $sample = array_fill(0, $count, 1.0 / $count); } else { array_walk($sample, function (&$feature) use ($norm1): void { $feature /= $norm1; }); } } private function normalizeL2(array &$sample): void { $norm2 = 0; foreach ($sample as $feature) { $norm2 += $feature * $feature; } $norm2 **= .5; if ($norm2 == 0) { $sample = array_fill(0, count($sample), 1); } else { array_walk($sample, function (&$feature) use ($norm2): void { $feature /= $norm2; }); } } private function normalizeSTD(array &$sample): void { foreach (array_keys($sample) as $i) { if ($this->std[$i] != 0) { $sample[$i] = ($sample[$i] - $this->mean[$i]) / $this->std[$i]; } else { // Same value for all samples. $sample[$i] = 0; } } } }