Phpml\Preprocessing\Normalizer::normalizeL1 PHP Method

    private function normalizeL1(array &$sample)
    {
        $norm1 = 0;
        foreach ($sample as $feature) {
            $norm1 += abs($feature);
        }
        if (0 == $norm1) {
            $count = count($sample);
            $sample = array_fill(0, $count, 1.0 / $count);
        } else {
            foreach ($sample as &$feature) {
                $feature = $feature / $norm1;
            }
        }
    }