weighted linear fit

[rg81]

Hello,

I'm new in this forum and unfortynately I'm not so confident with LabView.

Now I'm working with LabView 7.1 and I have a normal linear fit in my program. What I would like to do is change this fitting with a weighted linear fit.

Searching a bit in the web I found that in the version 8 there is already a VI for this fitting. I guess should be possible with a bit of math to write a subVI, but I have some problem to estimate the weights. is someone can help me?

And just another question: which of these fitting methods is the best:

-least square

-Least Absolute Residual

-Bisquare

Thanks

[Kurt_NISalesEngineer]

Hi laser81,

Thanks for posting your query on the National Instruments forums.

If you are new to LabVIEW then I would like to strongly recommend that you consider pursuing the LabVIEW Basics courses. The LabVIEW Basics 1: Introduction course is part of a series of courses designed to build your proficiency with LabVIEW and help you prepare for NI LabVIEW certification exams.

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The context help for linear fit VI in LabVIEW version 7.1 states:

Finds the line values and the set of linear coefficients slope and intercept, which describe the line that best represents the input data set using the least-squares solution.Finds the line values and the set of linear coefficients slope and intercept, which describe the line that best represents the input data set using the least-squares solution.

The context help for linear fit VI in LabVIEW version 8.2 states:

Returns the linear fit of a data set (X, Y) using the Least Square, Least Absolute Residual, or Bisquare method

If you then click the detailed help link in the context help window it will fire up the LabVIEW help document file where the help file explains the differences between

Least Square

, Absolute Residual and Bisquare method and equations are given.

I have attached the help file to this forum. Have you considered upgrading to the latest release of LabVIEW? It is jam packed with even more technology.

Check out the release notes for more information on what’s new with a particular release. Please goto www.ni.com/manuals

I have also found a similar discussion forum link that might be offer some help on the issue this explains a programmatic approach to curve fitting using low level VI’s in LabVIEW.

http://forums.ni.com/ni/board/message?board.id=170&message.id=181569&requireLogin=False

I hope this helps

Best Regards,

Kirtesh Mistry

National Instruments UK & Ireland

[Kurt_NISalesEngineer]

in the help file attached goto Context menu > VI & function reference > mathematics VI's > filtering VIs > linear fit

[altenbach]

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@Kurt NI AE wrote:

in the help file attached goto Context menu > VI & function reference > mathematics VI's > filtering VIs > linear fit

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I think you meant fitting VIs. 😉

[rg81]

Thanks Kurt NI AE for your help.

I tried to open the attached help file but I couldn't. I was thinking to install the LabView 8 but I guess is more complicate and now my system is working properly so, i'm a bit afraid from the idea to change everything. 

I was on the idea to use a General LS Linear FIt to make a weighed linear fit, but i'm not sure it will work.

Thanks