How to find x values from a given y value.

[Edithvvalle]

I have an array of values that simulate a graded potential/action potential graph. Depending on the values given by the user, my Waveform graph plots this array. However, I need to find the x value (in this case, time) at which the graph crosses a threshold. Since it's a graph that acts like a sine wave, sometimes it crosses the threshold twice or even more. 

[PatrickLye]

You should show some code.

Typically I keep time values in an asrray with my data in a situation like this. Then I can simply do a comparison on the amplitude to find when something achieves what I'm looking for, whether that is and amplitude, falling, or rising, and then the same index in the time array is where my time value is.

[zou · Accepted solution]

Have you tried threshold 1d Array yet ?

Use a loop the find all crosses.

[Edithvvalle]

It wasn't working earlier when I tried it, but it just did. Thank you so much!!

[ThuyHoai]

Hi, I have tried "threshold 1D Array" to find the 2 interpolated x-values at one certain y-value with for-Loop and while - Loop. But I get only the first x-value (or 2 the same x-value) in the output Array . Can you please tell me how I can fix this Problem?

I have also tried with the Cursor Y at the exact value -45dB but actually I don't know how to fix Cursor Y exactly at one certain Y-value.

(I am learning Labview just for few days and not yet familiar with all functions. Thanks for you help).

Thuy