[kamocat]

I'm using pixels in a picture, so I'm dealing with the 4th quadrant with the y axis negated.
And you're right. It should y÷x (rise÷run). Still doesn't seem to work, unfortunately.
I might try building a VI to find the closest match to any given real number so that I can use an array for this instead of the atan function.

EDIT:
For simplification (and because at this point I just don't need 360 divisions), I'm using 24 divisions (every 15 degrees). I might change it to 72 or 360 later.