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Read from graph

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.

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Message 1 of 8
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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.

Cory K
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Message 2 of 8
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Are you referring to a "waveform chart" or a "waveform graph" It is easy to confuse those two


Besides which, my opinion is that Express VIs Carthage must be destroyed deleted
(Sorry no Labview "brag list" so far)
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Message 3 of 8
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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

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Message 4 of 8
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You can interpolate to find points in between the ones you already have:

interpolate.PNG

 

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
Cory K
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Message 5 of 8
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Hi Cory,

 

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

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Message 6 of 8
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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?

Cory K
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Message 7 of 8
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Perhaps looking at the Get Y Value example will help you.
--
Tim Elsey
Certified LabVIEW Architect
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Message 8 of 8
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