The Origin Forum
File Exchange
Try Origin for Free
The Origin Forum
Home | Profile | Register | Active Topics | Members | Search | FAQ | Send File to Tech support
Username:
Password:
Save Password
Forgot your Password? | Admin Options

 All Forums
 Origin Forum
 Origin Forum
 Curve fitting
 New Topic  Reply to Topic
 Printer Friendly
Author Previous Topic Topic Next Topic Lock Topic Edit Topic Delete Topic New Topic Reply to Topic

Material Doc

Germany
1 Posts

Posted - 06/07/2014 :  1:15:37 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Hi,
I have curve that seems half gaussian and half Lorentz. I have following questions in this regard.
1) I want to calculate its FWHM?
2) In Gauss fit we get FWHM directly but in Lorentz we get only W value. How we can get FWHM from Lorentz fit ?

Atif

SeanMao

China
288 Posts

Posted - 06/09/2014 :  12:40:38 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi Atif,

For question (1), the direct way to obtain the FWHM of a peak in regardless of whether the actual function to describe the peak is known or not, that is Quick Peaks Gadget.

Please refer to following link for how to use Quick Peaks Gadget to obtain FWHM of your peak:
http://www.originlab.com/doc/Tutorials/Quick-Peak-Gadget

Alternatively, you can fit your peak to obtain FWHM.
From your description, I suspect your peak might be the type what we called asymmetric Gaussian peak which looks like “half Gaussian” and “half Lorentzian”. If so, you can refer to following tutorials for the solution to fit your peak using a piecewise function and obtain FWHM:

http://www.originlab.com/doc/Tutorials/UDF-Quote-BuiltInFunc

If it is not a asymmetric gaussian peak as I assumed, you can always define a piecewise fitting function with half as Lorentz and half as gauss and use the fitting width w1, w2 to calculate FWHM. An example is shown in the link below:

http://www.originlab.com/doc/Tutorials/Fitting-Piecewise-Linear

For question (2), Gauss fit FWHM is proportional to w with a factor sqrt(2 * ln(2)) while Lorentz fit FWHM is equal to w. The reference materials can be found in our websites:

http://www.originlab.com/doc/Origin-Help/Gauss-FitFunc

http://www.originlab.com/doc/Origin-Help/Lorentz-FitFunc

Please feel free to post back for further questions!

Thanks!

Sean

OriginLab Tech. Service

Edited by - SeanMao on 06/09/2014 12:43:51 AM
Go to Top of Page
  Previous Topic Topic Next Topic Lock Topic Edit Topic Delete Topic New Topic Reply to Topic
 New Topic  Reply to Topic
 Printer Friendly
Jump To:
The Origin Forum © 2020 Originlab Corporation Go To Top Of Page
Snitz Forums 2000