public function columnMultiply(int $nᵢ, int $k) : Matrix
{
if ($nᵢ >= $this->n) {
throw new Exception\MatrixException('Column to multiply does not exist');
}
if ($k == 0) {
throw new Exception\BadParameterException('Multiplication factor k must not be 0');
}
$m = $this->m;
$R = $this->A;
for ($i = 0; $i < $m; $i++) {
$R[$i][$nᵢ] *= $k;
}
return MatrixFactory::create($R);
}