See Release Notes
Long Term Support Release
Differences Between: [Versions 310 and 401] [Versions 311 and 401] [Versions 39 and 401]
1 <?php 2 3 declare(strict_types=1); 4 5 namespace Phpml\FeatureSelection; 6 7 use Phpml\Exception\InvalidArgumentException; 8 use Phpml\Math\Matrix; 9 use Phpml\Math\Statistic\Variance; 10 use Phpml\Transformer; 11 12 final class VarianceThreshold implements Transformer 13 { 14 /** 15 * @var float 16 */ 17 private $threshold; 18 19 /** 20 * @var array 21 */ 22 private $variances = []; 23 24 /** 25 * @var array 26 */ 27 private $keepColumns = []; 28 29 public function __construct(float $threshold = 0.0) 30 { 31 if ($threshold < 0) { 32 throw new InvalidArgumentException('Threshold can\'t be lower than zero'); 33 } 34 35 $this->threshold = $threshold; 36 } 37 38 public function fit(array $samples, ?array $targets = null): void 39 { 40 $this->variances = array_map(static function (array $column): float { 41 return Variance::population($column); 42 }, Matrix::transposeArray($samples)); 43 44 foreach ($this->variances as $column => $variance) { 45 if ($variance > $this->threshold) { 46 $this->keepColumns[$column] = true; 47 } 48 } 49 } 50 51 public function transform(array &$samples, ?array &$targets = null): void 52 { 53 foreach ($samples as &$sample) { 54 $sample = array_values(array_intersect_key($sample, $this->keepColumns)); 55 } 56 } 57 }
title
Description
Body
title
Description
Body
title
Description
Body
title
Body