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ramcd
USA
4 Posts |
 Posted - 12/14/2014 : 7:19:39 PM
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I have location vs time data and want to obtain speed by curve fitting. The measured time has uncertainty while the locations do not. The data with time on x-axis and locations on y-axis seem to follow an exponential relation. So I am trying to curve fit an exponential curve keeping the time data on x-axis and locations on y-axis. How do I include the error in time (which is on x-axis) in the fitting routine?
rcd |
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Shirley_GZ
China
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Posted - 12/14/2014 : 10:24:20 PM
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Hi,
Since Origin 9.1, OriginPro supports ODR (Orthogonal Distance Regression), you can use it to do fitting with X error.
Any problem, please let me know.
Thanks,
Shirley
Originlab Technical Service Team |
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ramcd
USA
4 Posts |
Posted - 12/14/2014 : 11:17:27 PM
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Hello,
Thank you for helping out. I tried using the ODR algorithm to fit an exponential curve- firstly by not including the error bounds, and secondly by including the error bounds. However, I am getting exactly same curve fits, statistics of fit, etc. While neglecting the errors, I select 'no weights' option in the Data Selection menu of the NLfit program. On the other hand, to include the errors I first set the error column as 'x-error', then select the 'Use Each Range Setting' option in NLfit. I run the curve fitting routine, but get exactly same fits and statistics in both the cases. Am I missing out on something?
To help you, I attache a snapshot of my data in OriginPro
rcd |
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ramcd
USA
4 Posts |
Posted - 12/14/2014 : 11:34:54 PM
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Just an update, the result doesn't change even if I vary the errors in column C. It seems that the error bounds are somehow not getting included in the fitting routine...
rcd |
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Shirley_GZ
China
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Posted - 12/15/2014 : 12:42:36 AM
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Please tell me which function you are using to fit the data. Or send us the project via tech@originlab.com and quote this post.
Originlab Technical Service Team |
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ramcd
USA
4 Posts |
Posted - 12/15/2014 : 01:12:45 AM
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quote:
Originally posted by Shirley_GZ
Please tell me which function you are using to fit the data. Or send us the project via tech@originlab.com and quote this post.
Originlab Technical Service Team
sent the project file
rcd |
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Topic |
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Curve fitting data with x error bounds