Fig. 3.

Softmax output for three sleep stages (Wake, REM, N2).

This figure illustrates that the softmax output spans a hyper-plane (in 3D a 2D hyper-plane with 3 corners). Note that the possible outputs lie in the volume below the hyper-plane. Not all points lie on the plane as confusions with sleep stage N3 or N1 cannot be shown in a 3D plot. Thus, if the softmax output would for example point to sleep stage N3 the point would lie near the origin (0,0,0). Note that absolute coordinates of points in MDS projections have no particular meaning other than scaling relative distances between any pair of points.