how to manipulate a svg matrix with javascript

how can I simply access a svg element, read the matrix and execute the rotation or transformation on the matrix objec.

I read the matrix from the element

let matrix = elements[index].getAttribute('transform');

I got

matrix(1 0 0 1 513.1588 411.1249)

Now I want to add something to the x value, and pass this transformation to anaother element.

 newElement.setAttribute('transform',matrix);

how can i make an matrix object to manipulate?

edited: I tried the var matrix = svgElement.createSVGMatrix()´(posted below) but I can't access simple elements. Like I understand the API, the createSVGMatrix is used for elements