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OriginBeginner
Germany
4 Posts |
 Posted - 10/30/2019 : 06:40:45 AM
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Hi there :)
I have to fit 5 data points as best as possible (exp(x) or 1/x - behavior) and extrapolate the curve a little. Not sure how I can upload a screenshot here directly,
so here is a link of what I have so far: https://ibb.co/QHC0z05
now what I need to do is the following:
- add a horizontal line for B = 1 (just as a linear function)
- extrapolate or continue the fitted exponantial function to the left,
at least until it intersects with that linear function at B = 1,
because ultimatelly I need to get the x-value (A) of the intersection.
Background: This is the Zisman-Method for obtaining a value for the surface energy
of a solid polymer sample.
I never used Origin before, so I have little to no clue .. ^^
Also, what do you think about R^2 = 98963 in this case? Is it a reasonable fit?
How can I tell? My idea was to try several fits and just choose the one with the biggest R value.
Hence, I was wondering if there is some sort of algorythm in Origin that automatically tries all the
fit functions and returns the best fit? ^^
Thank you so much,
hope I explained well enough :)
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YimingChen
1691 Posts |
Posted - 10/30/2019 : 09:00:58 AM
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Hi,
For your first question, basically you are looking for the x value of the point on the curve where its y value is 1. Please go to the Nonlinear Curve Fit dialog. (Click the green lock on the up-left of your report sheet and select Change Parameter). Under Settings tab in the dialog, select Find X/Y. Check the box Find X from Y in the right. Click Done to close the window. Then you will see a new worksheet with name FitNLFindXfromY1. You can simply enter a y value 1 in A[1] cell, it will get you the x value.
For your second question, the R^2 value is pretty good and the fitting is converged. To compare different models, please try the app Rank Models in Origin:
https://www.originlab.com/FileExchange/details.aspx?fid=440
Thanks,
James
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Edited by - YimingChen on 10/30/2019 09:08:26 AM |
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OriginBeginner
Germany
4 Posts |
Posted - 10/30/2019 : 2:16:59 PM
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Thank you very much!!
I did as you said and find the worksheet,
yet it does not calculate an X value for any given Y value,
that is not part of the fitted function. Looks like I do have
to "continue" the fitted curve to the left somehow?
here the result: https://ibb.co/5LfjB1s
Do you know how I can do that?
Again thank you so much, |
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OriginBeginner
Germany
4 Posts |
Posted - 10/30/2019 : 2:33:23 PM
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I just found this:
https://www.youtube.com/watch?v=rz5nKH9sn3I
exactly what I need haha,
but it seems not be a built-in in the latest version anymore..
can I download it somewhere? I mean the template:
Interpolate X or Y.ogw
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YimingChen
1691 Posts |
Posted - 10/31/2019 : 09:08:57 AM
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Hi,
The worbook template is still there. Please select menu File->New->Workbook..., you will find Interpolate X or Y under System Templates tab.
James |
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Topic |
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Nonlinear fit and extrapolation