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<?php
namespace Chippyash\Math\Matrix\Derivative;
use Chippyash\Math\Matrix\NumericMatrix;
use Chippyash\Math\Type\Calculator;
use Chippyash\Type\Number\FloatType;
use Chippyash\Matrix\Traits\AssertMatrixIsNotEmpty;
use Chippyash\Matrix\Traits\AssertMatrixIsSquare;
class Trace extends AbstractDerivative
{
use AssertMatrixIsNotEmpty;
use AssertMatrixIsSquare;
public function derive(NumericMatrix $mA, $extra = null)
{
if ($mA->is('singleitem')) {
return $mA->get(1,1);
}
$this->assertMatrixIsNotEmpty($mA, 'No trace for empty matrix')
->assertMatrixIsSquare($mA, 'No trace for non-square matrix');
$tr = new FloatType(0);
$size = $mA->rows();
$data = $mA->toArray();
$calc = new Calculator();
for ($x = 0; $x < $size; $x++) {
$tr = $calc->add($tr, $data[$x][$x]);
}
return $tr;
}
}