You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: shadedplot.m
    path of file: ./repos/erplab/functions
    
    the code of the file until where you have to start completion: function [ha hb hc] = shadedplot(x, y1, y2, varargin)

% SHADEDPLOT draws two lines on a plot and shades the area between those
% lines.
%
% SHADEDPLOT(x, y1, y2)
%   All of the arguments are vectors of the same length, and each y-vector is
%   horizontal (i.e. size(y1) = [1  N]). Vector x contains the x-axis values,
%   and y1:y2 contain the y-axis values.
%
%   Plot y1 and y2 vs x, then shade the area between those two
%   lines. Highlight the edges of that band with lines.
%
%   SHADEDPLOT(x, y1, y2, areacolor, linecolor)
%   The arguments areacolor and linecolor allow the user to set the color
%   of the shaded area and the boundary lines. These arguments must be

    
function [ha hb hc] = shadedplot(x, y1, y2, varargin)

% SHADEDPLOT draws two lines on a plot and shades the area between those
% lines.
%
% SHADEDPLOT(x, y1, y2)
%   All of the arguments are vectors of the same length, and each y-vector is
%   horizontal (i.e. size(y1) = [1  N]). Vector x contains the x-axis values,
%   and y1:y2 contain the y-axis values.
%
%   Plot y1 and y2 vs x, then shade the area between those two
%   lines. Highlight the edges of that band with lines.
%
%   SHADEDPLOT(x, y1, y2, areacolor, linecolor)
%   The arguments areacolor and linecolor allow the user to set the color
%   of the shaded area and the boundary lines. These arguments must be
%   either text values (see the help for the PLOT function) or a
%   3-element vector with the color values in RGB (see the help for
%   COLORMAP).
%
%   [HA HB HC = SHADEDPLOT(x, y1, y2) returns three handles to the calling
%   function. HA is a vector of handles to areaseries objects (HA(2) is the
%   shaded area), HB is the handle to the first line (x vs y1), and HC is
%   the handle to the second line (x vs y2).
%
%   Example:
%
%     x1 = [1 2 3 4 5 6];
%     y1 = x1;
%     y2 = x1+1;
%     x3 = [1.5 2 2.5 3 3.5 4];
%     y3 = 2*x3;
%     y4 = 4*ones(size(x3));
%     ha = shadedplot(x1, y1, y2, [1 0.7 0.7], 'r'); %first area is red
%     hold on
%     hb = shadedplot(x3, y3, y4, [0.7 0.7 1]); %second area is blue
%     hold off

% plot the shaded area
y = [y1; (y2-y1)]';
ha = area(x, y);
set(ha(1), 'FaceColor', 'none') % this makes the bottom area invisible
set(ha, 'LineStyle', 'none')

% plot the line edges
hold on
hb = plot(x, y1, 'LineWidth', 1);
hc = plot(x, y2, 'LineWidth', 1);
hold off

% set the line and area colors if they are specified
switch length(varargin)
        case 0
        case 1
                set(ha(2), 'FaceColor', varargin{1})
        case 2
                set(ha(2), 'FaceColor', varargin{1})
                set(hb, 'Color', varargin{2})
                set(hc, 'Color', varargin{2})
        otherwise
end