Linear fit between two cursors from a signal from a NI-instruments via DAQ-Assistant

Hi !
I'm currently having som problem with my labview code. I'm trying to make regression on a specific part of my graph. The graph consist of a signal gathered from a NI cDAQ-9178. Currently I can get the live data in a graph (Raw Signal) and then "zoom in" to the part of the graph that im intrested in by two cursors and then display the results in a new graph (Adjusted Signal). Now a want to make regresion in the new graph. How can i do this the best way ?
To be noted I'm a beginner of labview so my code maybe a bit off.
Best regards Maurlind
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Attachments:
Rawsignal test.vi ‏245 KB
rawsignal test.png ‏64 KB

Hi maurlind,
I got it, the function that derived the linear fit couldn't handle that large numbers on the x-axis. I edited the VI so that the large number is suctracted for the fit, i.e. the array will now begin at zero time for the fit. It will not affect your plots though, only the algorithm .
Try it now with the files I provided. The file "pm_mod2_Rawsignal test.vi" should be used with "test3.lvm" (your data). The file "pm_mod3_Rawsignal test.vi" is the same as "pm_mod2_Rawsignal test.vi", but it is arranged to work with the simulated data. The file "test3.lvm" is your data, but the file is slightly edited to work on my system.
Edit "pm_mod3_Rawsignal test.vi" to fit with your acquired signal as you did with the first file you got from me.
Attachments:
1412794.zip ‏483 KB

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Attachments:
Linear Fit Implementaion.PNG ‏44 KB

phanikiran wrote:
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How can I get extract the data between two cursors on an XY graph

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Solved!
Go to Solution.

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Attachments:
v603.png ‏320 KB
v603.vi ‏186 KB

Jeff Bohrer wrote:
Basic math gives me a bit of pause on this approach. You are sampling at 50 times the frequency of interest so you get 50 samples per cycle. your phase resolution is 1/50th cycle or 7.2 degrees +/- noise. You will need to samlpe faster to reduce phase resolution or average multiple readings (at a time cost that is signifigant)
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An interesting view. the sine wave can indeed be looked as a second harmonic of the square wave. I will implement your idea and get back to you as soon as I get some results. But since I have very limited knowledge of signal processing, it might take me a while to get my hear around the solution you mentioned.

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