Finding a Y value for a given X value?

[altenbach]

Don't overcomplicate things!

It would be much simpler if you would create an array of xy points (as you already hinted in the first post!). Now everything works directly as expected. See for example this old post. No "threshold array" function needed! 😄

[RavensFan]

I had never seen that implementation of Interpolation before.  I'll have to use that in the future.

[altenbach]

It is well documented in the help but usually overlooked, especially since the function is located in the array palette and the default input is a plain 1D array. 😄