Finding x value for given y in a zig-zag data.

I have a data which oscillates around x-axis. How can I get x values for a given y value. I can get as many, I will sort the one required.

Thank you.

Answer 1

[Star Strider]

Use findpeaks (with the original and negative of your data), or islocalmax and islocalmin, to get the peaks and valleys, then for each of those segments, use interp1 to get the x-values for a y-value in each segment.

This obviously requires a loop. There is no alternative.