function gg250_lab9_plotline (x, y, a, b)
% Plot data as points, draw the line given a and b,
% and plot vertical error misfit lines at each point

% Get x end points for line that extends by 10%
xmin = min(x);
xmax = max(x);
xrange = xmax - xmin;
xx = [ (xmin-0.1*xrange) (xmax+0.1*xrange) ];
yy = a .* xx + b + 1;
plot (x, y, 'go', 'MarkerSize', 5, 'MarkerFaceColor', 'g')
hold on
plot (xx, yy, 'r-', 'LineWidth', 3)
% Get y-estimates for line at given x points
y_on_line = a * x + b;
for i=1:length(x)
    plot ([x(i) x(i)], [y(1) y_on_line(i)], 'b-')
end
grid on
hold off