How can I do curve fitting from a xy graph?

[mei0512]

Hello, after I can get real-time data curve by using xy graph

I want to do curve fitting on it, but I failed......

I tried express curve fitting  & nonlinear curve fit but they just didn' work

How could I apply sigmoid curve fitting on it........?

please give me some advice ,  thanks!!

[mtwar]

Hi!

You have to first convert XY values to the Waveform - Curve Fitting Signals accept waveform as parameter.

Try to follow this instruction:

http://digital.ni.com/public.nsf/allkb/53E96C82FF016576862574670052585D

I would like to try it by myself to help you better in case this solution doesn't work, can you please share your X and Y input?

Marcin

[mei0512]

ok,  just like this

after press the "run" button, then you have to press the start to get the data, and press it again to stop recording data.  then there is a curve  on the right upper screen , I want to do curve fitting on it.......

please help me!!  thanks

[mtwar]

Can you please me send the pure data - X and Y array? I don't have IMAQ to run your VI.

To create these Arrays you can just use Build Array function with feedback node.

Then when you stop your VI just right click on indicator and choose Data Operations -> Copy Data, paste the date to excel and attach it

Marcin

[mei0512]

I followed what you said, but after pressing "copy data"and paste to excel, there is only a picture,  the data is from export to excel

[Daikataro]

Have you tried feeding the X/Y data as a 2d array to the regression solver example VI? It is pretty well made, and perfectly illustrates the functionality of LabVIEW's regression tools; matter of fact I am using it to get adjustment curve equations for instrument calibration with minimum modifications to the code.

[mtwar]

Yes, of course you are right, it should be export to excel.

I have created some overview VI for you. Save text file and VI in the same directory and see how it works. Basically I have used method from the link I have sent previously.

My note about your VI is that you should use array of numbers to create XY graph, not just one number. You can use the array you have created for me.

Sorry for the mess, I'm in hurry. I hope you can extract what you need from it.