azimuth

      set view azimuth <angle-in-degrees>

The setting of azimuth affects the orientation of the z axis in a 3D graph (splot). At the default azimuth = 0 the z axis of the plot lies in the plane orthogonal to the screen horizontal. I.e. the projection of the z axis lies along the screen vertical. Non-zero azimuth rotates the plot about the line of sight through the origin so that a projection of the z axis is no longer vertical. When azimuth = 90 the z axis is horizontal rather than vertical. During interactive viewing, hot-key z resets azimuth to 0.