Fitting a Lorentzian function to xy data

[QuantumPenguin]

Hello all,

I am trying to fit a lorentzian to my data (see attached for a sample). The peak, is extremely narrow, but it is for sure a lorentzian. I was trying to make the example I found in this post from altenbach work:

https://forums.ni.com/t5/LabVIEW/Lorentzian-Curve-fitting/m-p/208738#M118192

Unfortunately I can't get anything out of this 

Can anyone suggest or provide a rough example?

[altenbach]

No, don't use this ancient code. This is from a time where the LabVIEW nonlinear fitting tools were a bit limited.

If you have a single lorentzian, you can estimate the position, vertical offset, height and width easily from the data. All you need is "nonlinear curve fit" and a model VI that generates a lorentzian from the same x-values as your data.

You probably need at least 4 parameters: area, position, width, offset.

I would recommend to start here.

[QuantumPenguin]

Ah, I see! It's still a nice program though. Thanks I will take a look at these posts as you suggest.

[altenbach · Accepted solution]

Here's a very rough draft that seems to work just fine (LabVIEW 2014). It is hard to define a Lorentzian with about 5 noisy points 😄

[QuantumPenguin]

That's really excellent, it fit the data first time with no effort at all -- top man!!

[Avral]

thanks, really helpful...