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Bulliwyf
USA
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 Posted - 01/26/2006 : 11:35:32 PM
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Origin Version (Select Help-->About Origin): 7SR4
Operating System: WINXP
Hi,
I use Origin for several years now and I recently upgraded my origin 6.0 to 7.
Since this upgrade I can not do a sigmoidal fitting with an error bars weighting whatever datasheet I use. Everytime a message appears saying : "There is (are) zero or small error value(s) (<1.0E-153) and this is not consistent with the chosen weighting method" even on data I successfuly fitted with weighting with Origin 6.0. That's bugging me because I've done this numbers of time before. This is very frustrating and I can not see what is wrong. I can fit with no weighting but this is not what I want.
Thanks for any help.
David |
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easwar
USA
1964 Posts |
Posted - 01/27/2006 : 09:38:22 AM
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Hi David,
When you have data with error bars plotted and you use the analysis menu item "Fit Sigmoidal", the weighting method is set to Instrumental weighting by default, and the weights are computed as (1/error^2).
Thus if an error value is (very close to) zero, this weighting method does not work because 1/value^2 is too large or undefined. In version 6.0 such values were being ignored, which is incorrect, and so we added this check in 7.0 and onwards.
You should first determine if instrumental weighting is the appropriate weighting method for your measurement/data. There are other weighting methods available, and can be chosen in the NLSF tool. You can bring up the NLSF tool and then after selecting fitting function and assinging data, go to the Options->Control menu item where you can set the weighting method. Press F1 on that page to read about different weighting options and what they mean. Please contact tech support directly if you need more help.
Easwar
OriginLab
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Bulliwyf
USA
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Posted - 01/27/2006 : 11:00:56 AM
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Thank you very much, you just solved my problem
David |
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Error weighting fitting problem