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Miranda01
Germany
5 Posts |
 Posted - 02/26/2018 : 06:00:59 AM
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Origin Ver. and Service Release (Select Help-->About Origin): OriginPro 8 SR0
Operating System:Win10
Hi,
Im fitting a data set with f=1,2+(k*ln(x)), with confidence interval of 95%.
I have plots of my data generated with sigma plot, where the starting point of the confidence bands are fixed at 1,2.
Do I have the possibility to do that in origin as well?
Thanks for your help,
Miranda
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arstern
USA
237 Posts |
Posted - 02/26/2018 : 09:21:36 AM
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Hi Miranda,
In Origin you can create a User Defined Fitting function. Please see tutorial: https://www.originlab.com/doc/Tutorials/UserDef-FitFunc
Under Fitted Curves in Settings you can select Confidence Bands and Prediction Bands option.
Under Parameters you can select the Fixed box for the initial y0= 1.2
Hope this helps,
Aviel
OriginLab |
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Miranda01
Germany
5 Posts |
Posted - 02/28/2018 : 04:25:30 AM
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Hi Aviel,
thanks for your answer. It does fix the y0 of the fit at 1.2, but it does not fix the confidence bands at this value.
Maybe this is not possible in Origin?
Regards,
Miranda |
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arstern
USA
237 Posts |
Posted - 02/28/2018 : 10:03:37 AM
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Hi Miranda,
Would you please send your data and/or project file at tech@originlab.com? It will be easier for me to understand what you want to do by taking a look at your data.
Thanks,
Aviel |
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Miranda01
Germany
5 Posts |
Posted - 03/01/2018 : 05:08:09 AM
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Hi Aviel,
I just sent the Mail.
Thanks, Miranda |
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arstern
USA
237 Posts |
Posted - 03/01/2018 : 1:07:54 PM
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Hi Miranda,
Thank you for sending the file. I was able to reproduce the plot from the example you sent me.
I will show you how I setup the fitting function so that hopefully you can recreate as well.
1. I first plot all three datasets with the error bars.
2. I then select one of the plots and select -> Analysis -> Fitting -> Nonlinear Curve Fit to open up the Nonlinear Fit Dialog
3.Under Settings -> Select Fitted Curves.
4. For X Data Type Select -> Span to Full Axis Range for Range tab. This allows the fit to extend the entire axis rather than just the range of the points.
5. Select Confidence Bands and keep 95% for Confidence Level.
6.Select Data Selection
7. Because error bars are plotted you will need to specify whether to include the standard error into the fit. If you select No Weighting this means you will not be including the standard error into the fit. This option matches the graph that you sent me.
7. If you decide to account for standard error in your fitting results. You will select Weight type Instrumental and select corresponding error data. See graph below. This changes the result of the confidence bands.
 .
8. That's pretty much it. Select Fit.
9. I created 3 user defined equations and used each equation according to the data.
For example:
For fit TCE I input:
y = 1.20+((k)*ln(x))
k = parameter (not fixed)
Below are my table results for each fit:
10. Please note that I did not set the confidence interval at starting a point. The confidence interval was calculated based off how variable the data is to the fit and the standard error (if included). If you input the equations as for example y=1.2+(k*ln(x)) then it makes sense that the Upper and Lower confidence band at x = 0.93151 will be both 1.2 because the y0 in the equation is set to 1.2 which is also the value in your dataset.
Here's an example where the confidence band does not converge at x = 0.93151. Within the user defined equation I set y = y0+(k*ln(x)). Origin guessed the parameter for y0 as 0.94. Because the value 0.94 is different then the data value (1.2), the upper and lower confidence limit values provide different upper and lower bound values.
If you are still having difficulties after my post, I recommend installing the 21 day Evaluation License of Origin 2018 to see if it makes a difference. I noticed from your post that you are using OriginPro8 which is not very compatible with Windows 10.
Hope this helps!
Aviel |
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Miranda01
Germany
5 Posts |
Posted - 03/05/2018 : 05:53:23 AM
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Hi Aviel,
thank you for your answer. I try to give feedback as soon as possible.
Regards,
Miranda |
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Miranda01
Germany
5 Posts |
Posted - 03/08/2018 : 11:21:50 AM
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Hi Aviel,
it did not work with OriginPro 8 but I was successful with the Evaluation Version of OriginPro 2018.
Many thanks for your help!
Best, Miranda |
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Topic |
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fix confidence bands