WAVE HISTOGRAM displays a histogram of the heights of individual waves
derived from the vertical displacement timeseries. Individual waves
are identified using the crest-to-trough method, i.e. by calculating
the crest-to-trough difference between consecutive zero up-crossings.
For buoys operated by the Navy (e.g. 067, the SNI buoy), the user can
specify a height threshold and the plot will show the percentage of
waves that exceed the given threshold. The default threshold is
4 meters or 13 feet.
