H1 line, good help section, no example, date and author mentioned. The source is clean, but has no comments. Very flexible parsing of inputs with some error checks.
For run on old Matlab versions: plot(ax, ...) -> plot(x, y, varargin{:}, 'Parent', ax); I'd prefer LINE instead of PLOT, but this is a question of taste.
Summary: useful, clean, works really well.
Comment only