MATLAB: Creating upper and lower thresholds when graphing

graph thresholds

How do you create thresholds when graphing with red dotted lines.

after you plot the original data

hold on,
plot(x,y,'r--');

where x = [Xaxisstart Xaxisend] and y=[yaxisThresholdvalue yaxisThresholdvalue]

trapz(x,y)

xmin=0;
xmax=1;
ymin=0;
ymax=1;
plot([xmin xmax xmax xmin xmin],[ymin ymin ymax ymax ymin])

rectangle('position',[xmin ymin xmin xmax])