Trying to add horizontal line on a graph

So im trying to add a horizontal line to to show the mean gradient to the graph on the bottom.

The mean is -0.0714 and i want to draw this line as a dotted line. iv tried all sorts of things on this forum but cant seem to get it

Thanks in advance

Answer 1

[Walter Roberson]

XL = xlim();
plot( XL, [TheMean, TheMean])

[Jack Lakeman]

Thank you!

But it seems to draw a line 3/4 of the graph and not through the entire graph. And is there any way to change the colour and have it dotted?

It gives me an error message when i try to do it. i must be doing it wonrg

[Walter Roberson]

Example:

plot(x,y)
x = 1:30;
y = sin(x)+x;
TheMean = mean(y);
plot(x,y)
hold on
XL = xlim();
plot(XL, [TheMean TheMean], 'g--')
hold off