PLOT_LINES

plot_lines(xin) - Plots vertical lines at points defined on the x-axis using red solid lines and the current y-axis limits using a single line handle

plot_lines(xin,[a b]) - Plots the lines from a to b

plot_lines(xin,[],lntype) - Plots the lines using the current y-axis limits using the line type deined by lntype

h = plot_lines(xin,[a b],lntype) - Returns the handle to the vertcal lines

Ex.)
figure(1);clf;
plot(randn(1,1000));
x = [10 170 300 450 600 800 990];
hold on;
plot_lines(x,[],'b:');