How to set a horizontal line at one specific point on a plot?

Hello. How can I create a horizontal line at a specific point like that in the picture?

Answer 1

[Birdman]

For instance:

line([2.5,11.5],[-4,-4])

[Emanon]

2.5 is the starting point? Because when I set the starting point below zero the line doesn't appear

[Birdman]

Yes it is starting point and below zero you can not see the line because your x axis starts at 0.01

[Emanon]

I had to change that too eventually. Thank you very much.

[Birdman]

Has the answer worked for you? If so, you can accept it.

[Emanon]

Yes thank you. First time here. Didn't know.