Read from graph

[ander99]

Hi,

I would like to check whether is LV able to read Y axis values based on given X axis values. The graph is already plotted with few points.

[Cory_K]

Is your data in an array?

If so, you can use 'search array' to find the index of a given x value.

Then use 'index array' to find the y-value at that index.

If the y-value you want to find does not yet have an x-value,

you must either interpolate or extrapolate accordingly.

[Coq_Rouge]

Are you referring to a "waveform chart" or a "waveform graph" It is easy to confuse those two

[ander99]

Thank you for the fast replies from you guys. I attached my VI.

My problem is based on the graph i had. How do i get data for 20k based on the graph? I understand that the array to generate this graph do not have the data in the array. How should i go about doing this? Hope someone enlighten me.

Regards,

Ander

[Cory_K]

You can interpolate to find points in between the ones you already have:

The output array, yi, will be 2,000,000 points.

You can index the array, at 20,000 as you said, to find the y-value.

You an do the same for any value you would like to find.

Message Edited by Cory K on 06-17-2009 10:48 AM

[ander99]

Hi Cory,

I can't get 20k for the value of 43 based on the block diagram.

[Cory_K]

When I used the code I posted above, when I entered an x-value of 20,000

I got 41.444 back. Is that correct or no?

[elset191]

Perhaps looking at the Get Y Value example will help you.