Element.marker(x, y, width, height, refX, refY)

Creates a <marker> element from the current element To create a marker you have to specify the bounding rect and reference point:

Parameters

1. xnumber
2. ynumber
3. widthnumber
4. heightnumber
5. refXnumber
6. refYnumber

Returns: Element the <marker> element

You can specify the marker later as an argument for marker-start, marker-end, marker-mid, and marker attributes. The marker attribute places the marker at every point along the path, and marker-mid places them at every point except the start and end.