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 What algorithm is used for the Voigt function?		  New Topic  Reply to Topic
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zygote72

USA
2 Posts
Posted - 09/19/2014 :  4:38:42 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin 8.6.0 SR3
Windows 7-64bit SR1

I am wondering if there is any documentation on how Origin calculates the Voigt function.

There is no closed form for the integral and so it must be computed numerically. I have compared Voigts generated by Origin with equivalent Voigts generated by published algorithms [1,2]. I am getting errors in the Origin Voigts on the order of 2e-6 which is too large for my application. The errors are in the width and in step discontinuities in the wings after about twice the full width, especially when approaching the Gaussian limit.

[1] Weideman JAC. Computation of the Complex Error Function. SIAM Journal on Numerical Analysis. 1994;31:1497-518. http://dx.doi.org/10.1137/0731077
[2] Johnson SG. Faddeeva Package. http://ab-initio.mit.edu/wiki/index.php/Faddeeva_Package

lkb0221

China
497 Posts
Posted - 09/19/2014 :  4:45:42 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

Do you mean this one?
http://www.originlab.com/doc/Origin-Help/Voigt-FitFunc

Zheng
OriginLab
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zygote72

USA
2 Posts
Posted - 09/19/2014 :  4:49:59 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Yes.
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