Statistics.php

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<?php

declare(strict_types=1);

namespace ILIAS\Test\Statistics;

class Statistics
{
    private array $stat_data = [];
    private ?\ilTestEvaluationUserData $median_user = null;

    public function __construct(\ilTestEvaluationData $eval_data)
    {
        $median_array = array_map(
            fn(\ilTestEvaluationUserData $v): float => $v->getReached(),
            $eval_data->getParticipants()
        );

        $this->stat_data = array_values($median_array);
        sort($this->stat_data);

        if (($median_user_id = array_search($this->median(), $median_array)) !== false) {
            $this->median_user = $eval_data->getParticipant($median_user_id);
        }
    }

    public function getEvaluationDataOfMedianUser(): ?\ilTestEvaluationUserData
    {
        return $this->median_user;
    }

    public function min(): ?float
    {
        if ($this->stat_data === []) {
            return null;
        }

        return min($this->stat_data);
    }

    public function max(): ?float
    {
        if ($this->stat_data === []) {
            return null;
        }

        return max($this->stat_data);
    }

    public function count(): int
    {
        return count($this->stat_data);
    }

    public function sum_n(int $n): ?float
    {
        if ($this->stat_data === []) {
            return null;
        }

        $sum_n = 0;
        foreach ($this->stat_data as $value) {
            $sum_n += pow((float) $value, (float) $n);
        }
        return $sum_n;
    }

    public function sum(): ?float
    {
        return $this->sum_n(1);
    }


    public function sum2(): float
    {
        return $this->sum_n(2);
    }

    public function product_n(int $n): ?float
    {
        if ($this->stat_data === []) {
            return null;
        }

        if ($this->min() === 0) {
            return 0.0;
        }

        $prod_n = 1.0;
        foreach ($this->stat_data as $value) {
            $prod_n *= pow((float) $value, (float) $n);
        }
        return $prod_n;
    }

    public function product(int $n): ?float
    {
        return $this->product_n(1);
    }

    public function arithmeticMean(): ?float
    {
        $sum = $this->sum();
        if ($sum === null) {
            return null;
        }

        $count = $this->count();
        if ($count === 0) {
            return null;
        }
        return (float) ($sum / $count);
    }

    public function geometricMean(): ?float
    {
        $prod = $this->product(1);
        if (($prod === null) || ($prod === 0)) {
            return null;
        }
        $count = $this->count();
        if ($count === 0) {
            return null;
        }
        return pow((float) $prod, (float) (1 / $count));
    }

    public function harmonicMean(): ?float
    {
        $min = $this->min();
        if (($min === null) or ($min === 0)) {
            return null;
        }
        $count = $this->count();
        if ($count === 0) {
            return null;
        }
        $sum = 0.0;
        foreach ($this->stat_data as $value) {
            $sum += 1 / $value;
        }
        return $count / $sum;
    }

    public function median(): ?float
    {
        if ($this->stat_data === []) {
            return null;
        }

        $count = $this->count();
        if ((count($this->stat_data) % 2) === 0) {
            return ($this->stat_data[($count / 2) - 1] + $this->stat_data[($count / 2)]) / 2;
        }

        return $this->stat_data[(($count + 1) / 2) - 1];
    }

    public function rank(float $value): ?int
    {
        $rank = array_search($value, $this->stat_data);
        if ($rank === false) {
            return null;
        }

        return $this->count() - $rank;
    }

    public function rankMedian(): ?int
    {
        $count = $this->count();
        if ($count === 0) {
            return null;
        }

        if (($count % 2) === 0) {
            return $count / 2;
        }

        return ($count + 1) / 2;
    }

    public function quantile(float $n): ?float
    {
        $count = $this->count();
        if ($count === 0) {
            return null;
        }

        $nprod = ($n / 100) * $count;
        if (intval($nprod) != $nprod) {
            return $this->stat_data[ceil($nprod) - 1];
        }

        if ($nprod === 0.0) {
            return $this->stat_data[0];
        }

        if ($nprod === (float) $count) {
            return $this->stat_data[(int) $nprod - 1];
        }

        return ($this->stat_data[(int) $nprod - 1] + $this->stat_data[(int) $nprod]) / 2;
    }
}