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 Fitting data to equation		  New Topic  Reply to Topic
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mohamed1986

43 Posts
Posted - 06/17/2014 :  12:49:30 PM  Show Profile  Edit Topic  Reply with Quote  View user's IP address  Delete Topic
Origin Ver. and Service Release (Select Help-->About Origin): 9.1
Operating System: Win 7
Dear Friends,
Kindly, I have the attached equation, and I want to fit my x and y data to this equation to get the values of A and B
Could you please help me with that ?
y----------x
62.2040 361.9802
57.6240 360.6623
53.0280 359.0736
48.6790 356.8264

Thanks much
Edited by - mohamed1986 on 06/17/2014 12:50:40 PM

lkb0221

China
497 Posts
Posted - 06/17/2014 :  1:57:34 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

You can try to define a user-defined fitting function and do the fit.
http://www.originlab.com/doc/Origin-Help/UserDef-FitFunc
http://www.originlab.com/doc/Quick-Help/UserDefinedFittingFunction

Four points should be fine in your case for it only contains 2 parameters, but it will be better if you have more data for fitting.

Zheng
OriginLab
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mohamed1986

43 Posts
Posted - 06/17/2014 :  2:22:17 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks much for your help.
I have written the equation to be:
A*(x^2)/(x-241)+84*B*((407-x^2-407*x)/(x*(407-x)^2))
I think that there is error with this expression.

Could you please tell me about the A and B parameters, shall I put them in parameters or derived parameters section knowing that both A and B are constant?
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lkb0221

China
497 Posts
Posted - 06/17/2014 :  3:22:29 PM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Hi,

I tried your function and looks working fine.
The A and B should be "parameters".

"Derived parameters" are additional parameters computed using the fitted parameter values, for example, FWHM in Gauss.

Zheng
OriginLab
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mohamed1986

43 Posts
Posted - 06/19/2014 :  02:33:15 AM  Show Profile  Edit Reply  Reply with Quote  View user's IP address  Delete Reply
Thanks much for your kind help
Best regards
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