How to extract values from plot?

I created two plots using the fnplt function. One plot represents the chord length (c) over the radial position, the other the thickness (t) over the radial position (-> they both have the same x-axis).

I need to calculate the spar height h = c*t and plot h against the radial position.

How can I extract the c and t values at specific x-axis values (e.g. x=10, x=20, x=30)? Or perhaps an interpolation would make more sense in order to get a smoother graph?

Thanks in advance!

[KSSV]

https://in.mathworks.com/matlabcentral/answers/100921-how-do-i-extract-data-points-from-a-plot

[Lu Da Silva]

That doesn't answer my question.... I'd like to have the y-values for specific x-values.

[dpb]

interp1