2016-04-12 20:02:14 +00:00
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<?php
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declare (strict_types = 1);
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namespace Phpml\Metric\Distance;
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use Phpml\Exception\InvalidArgumentException;
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use Phpml\Metric\Distance;
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class Minkowski implements Distance
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{
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/**
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* @var float
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*/
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private $lambda;
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/**
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* @param float $lambda
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*/
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public function __construct(float $lambda = 3)
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{
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$this->lambda = $lambda;
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}
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/**
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* @param array $a
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* @param array $b
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*
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* @return float
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*
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* @throws InvalidArgumentException
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*/
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public function distance(array $a, array $b): float
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{
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if (count($a) !== count($b)) {
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throw InvalidArgumentException::sizeNotMatch();
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}
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2016-04-17 15:10:26 +00:00
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$distance = 1;
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2016-04-12 20:02:14 +00:00
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$count = count($a);
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for ($i = 0; $i < $count; ++$i) {
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$distance += pow(abs($a[$i] - $b[$i]), $this->lambda);
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}
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return pow($distance, 1 / $this->lambda);
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}
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}
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