StandardDeviation   A
last analyzed

Complexity

Total Complexity 8

Size/Duplication

Total Lines 48
Duplicated Lines 0 %

Importance

Changes 0
Metric Value
wmc 8
eloc 20
dl 0
loc 48
rs 10
c 0
b 0
f 0

2 Methods

Rating   Name   Duplication   Size   Complexity  
A population() 0 22 6
A sumOfSquares() 0 13 2
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<?php
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declare(strict_types=1);
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namespace Phpml\Math\Statistic;
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use Phpml\Exception\InvalidArgumentException;
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class StandardDeviation
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{
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    /**
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     * @param float[]|int[] $numbers
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     */
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    public static function population(array $numbers, bool $sample = true): float
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    {
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        $n = count($numbers);
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        if ($n === 0) {
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            throw new InvalidArgumentException('The array has zero elements');
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        }
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        if ($sample && $n === 1) {
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            throw new InvalidArgumentException('The array must have at least 2 elements');
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        }
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        $mean = Mean::arithmetic($numbers);
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        $carry = 0.0;
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        foreach ($numbers as $val) {
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            $carry += ($val - $mean) ** 2;
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        }
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        if ($sample) {
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            --$n;
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        }
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        return ($carry / $n) ** .5;
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    }
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    /**
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     * Sum of squares deviations
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     * ∑⟮xᵢ - μ⟯²
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     *
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     * @param float[]|int[] $numbers
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     */
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    public static function sumOfSquares(array $numbers): float
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    {
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        if (count($numbers) === 0) {
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            throw new InvalidArgumentException('The array has zero elements');
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        }
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        $mean = Mean::arithmetic($numbers);
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        return array_sum(array_map(
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            function ($val) use ($mean) {
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                return ($val - $mean) ** 2;
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            },
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            $numbers
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        ));
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    }
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}
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