| T O P I C R E V I E W |
| Material Doc |
Posted - 06/07/2014 : 1:15:37 PM
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 |
| 1 L A T E S T R E P L I E S (Newest First) |
| SeanMao |
Posted - 06/09/2014 : 12:40:38 AM
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
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