function h=vertical0(c)
%VERTICAL0  Draws a vertical line at x=0 on current plot.
%
%       VERTICAL0 draws a line at x=0 on the current plot using
%       the default color white.
%
%       VERTICAL0(C) does the above with the user specified 
%       color C.
%
%       H=VERTICAL0(C) returns the handle to the vertical line.
%
%

%       Mike Cook - NPS Oceanography Dept.,  MAR 94
%       Mike Cook - Modified program to return handle H.  Jan96
%       Mike Cook - Streamlined code abit.  Mar96.


defaultcolor = 'w';

if nargin == 1
    if isstr(c) ~= 1
        error(' The input color must be a string ')
    end
else
    c = defaultcolor;
end


axy = axis;    % Get max/min x and y axis limits.

h=line('Xdata',[0,0],'Ydata',[axy(3),axy(4)], ...
       'Color',c);

return
