Intersection point of a graph and horizontal line

i want to find the coordinates of a interseciton point of a graph and a horizontal line.

Is there an easy way to do it in Octave?
I heard it lacks a function that MatLab has which calculates that (idk if thats true tho).

Thanks in advance for answers,
xxxz.m (241 Bytes)

If the first gain variable is monotonic, then something like the following should work:

freq_intersect = interp1 (gain, freq, z, "linear") 

Works great!
Thanks so much