The graph simulates electric field lines
To create the graph, we prepare data of a half part. Once the graph is created and customized, it is duplicated to be another half part to make the whole circle, electric field lines from positive to negative charge.
We have prepared derivatives of the streamlines in the (x ,y) directions, which is calcuated from the electric field equation.
The U and V should be put in two matrix objects in a matrix sheet.