Depth of cut vs speed and power

So I have been trying to work out a better understanding of how speed and power affect depth of cut. I eventually hit upon the formula depth = (power * passes) / (speed * spot size) and have run a series of experiments to prove that this is in fact the case. Attached below is a picture of one test where I varied speed and power across a 2D grid and made a cast of the resulting cut. You can see all the tests at the post below, if you are curious.