| T O P I C R E V I E W |
| elvis_xia |
Posted - 01/02/2006 : 08:30:10 AM
Origin Version (Select Help-->About Origin):
Operating System:
I use the same fitting function to fit a group of data by diffenent fitting method. One result is done by Origin and the other is not. Now I want to compare the goodness of the two results.
I think the parameter chi^2/DOF can finish the work. But I have two question:
1. is the fitting result the same one by Origin?
one way is: analysis- non-linear curve fitting
the other is: tools - polynomial fit
2.the definetion of chi^2/dof is ?
sum(data point-fuction point)^2/dof, where dof=data point-number of parameter? |
| 3 L A T E S T R E P L I E S (Newest First) |
| minimax |
Posted - 01/05/2006 : 06:50:52 AM
Hi Elvis,
Origin 7.5 does not support weights in both coordinates. And we will add weights in both coordinates into linear fit in Origin version 8.
quote:
Thank you for your reply.
But I have another two queations.
The first is, is it true that Origin can only fit data with error in one coordinate? I think it seems that during my investigation.
The other is how to give chi^2 with weights in both coordinates?
Furthermore, I found that the fitting curve derived from the following two is the same.(I use 7.5 edition)
(1) tools- polynomial fit- setting(choose error as weight and use reduced chi^2)
(2)analysis -NLSF- advanced fitting tool - use control to set weight.
Edited by - elvis_xia on 01/03/2006 07:22:23 AM
Edited by - elvis_xia on 01/03/2006 07:25:36 AM
Edited by - elvis_xia on 01/03/2006 07:26:34 AM
Max
OriginLab GZoffice |
| elvis_xia |
Posted - 01/02/2006 : 10:38:20 PM
Thank you for your reply.
But I have another two queations.
The first is, is it true that Origin can only fit data with error in one coordinate? I think it seems that during my investigation.
The other is how to give chi^2 with weights in both coordinates?
Furthermore, I found that the fitting curve derived from the following two is the same.(I use 7.5 edition)
(1) tools- polynomial fit- setting(choose error as weight and use reduced chi^2)
(2)analysis -NLSF- advanced fitting tool - use control to set weight.
Edited by - elvis_xia on 01/03/2006 07:22:23 AM
Edited by - elvis_xia on 01/03/2006 07:25:36 AM
Edited by - elvis_xia on 01/03/2006 07:26:34 AM |
| Mike Buess |
Posted - 01/02/2006 : 09:22:38 AM
1. NLSF's Parabola fitting function with no additional constraints or weighting gives the same result as Tools > Polynomial Fit.
2. Correct for an unweighted fit. Otherwise multiply each term in the sum by the appropriate weight. Your expression for dof is correct.
Mike Buess
Origin WebRing Member |
