Phpml\Preprocessing\Imputer::getAxis PHP Method

    private function getAxis(int $column, array $currentSample) : array
    {
        if (self::AXIS_ROW === $this->axis) {
            return array_diff($currentSample, [$this->missingValue]);
        }
        $axis = [];
        foreach ($this->samples as $sample) {
            if ($sample[$column] !== $this->missingValue) {
                $axis[] = $sample[$column];
            }
        }
        return $axis;
    }