atan2

atan2(Y,X) returns the four quadrant inverse tangent, expressed in radians.

>> [x,y] = meshgrid(-5:5)
surf(x, y, atan2(y, x), struct('lineWidth', 0.1, 'pitch', 0.7))

[x:11x11 double]
[y:11x11 double]
[ans:1x1 struct]