Simultaneous display of the hypnogram from one healthy subject and the associated values of the features computed from each epoch. The red lines show wake, NREM 1 to 4, and REM sleep stages with respect to epoch numbers throughout the night's sleep (hypnogram). Because of simultaneous display, on the hypnogram wake and REM are at the levels of 500 and 250 ms, respectively. NREM 1 to 4 stages are shown at 400 to 100 ms levels, respectively. Blue, green, and black graphs indicate median (values are halved for better representation), interquartile range (iqr), and mean absolute deviation (mad) of RR values obtained from each epoch.