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darezzi
Yugoslavia
3 Posts |
 Posted - 06/19/2014 : 2:54:44 PM
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| I'm new to Origin, and I've tried finding the function for this, but it's nowhere to be found. Alternatively, I've tried making a custom function, but nothing shows up, so I'm guessing it doesn't work. |
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lkb0221
China
497 Posts |
Posted - 06/19/2014 : 3:10:56 PM
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Hi,
You can use Allometric1 (y=a*(x^b)) function, with b fixed to -1.
Zheng
Originlab |
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darezzi
Yugoslavia
3 Posts |
Posted - 06/19/2014 : 3:13:53 PM
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| Thanks! I still haven't worked out how to change a graph's parameters (like slope and intercept) after I've made it though. When I change it in the table, and click update table, nothing happens. |
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lkb0221
China
497 Posts |
Posted - 06/19/2014 : 3:20:23 PM
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Change a graph's parameters?
What are you trying to do want by that?
I thought you are making a fit. |
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darezzi
Yugoslavia
3 Posts |
Posted - 06/19/2014 : 6:10:56 PM
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| No, I managed to fit it, I was just asking if I make a mistake fitting, where do I change the graph? It seems to stay static after it's made. |
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lkb0221
China
497 Posts |
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Hideo Fujii
USA
1582 Posts |
Posted - 06/26/2014 : 11:16:42 AM
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Hi darezzi,
> I managed to fit it, I was just asking if I make a mistake fitting, where do I change the graph?
Seems you have already done fitting, and obtained the fitted curve; though you now want to
change the fitting parameters of the curve. First what you need to know is that the fitted curve
in the graph is the fitting result, STILL ASSOCIATED with the fitting, NOT a simply separate graph.
In other words, the fitted curve IS a fit result.
Many Origin users enjoy using its "recalculation" feature of the analysis tools, including fitting.
This allows you to change the initial parameter values, constraints, or even the function itself,
then you can recalculate to update the fitted curve. The following is a typical procedure of recalculation
of non-linear curve fitting after fitting originally:
1) Left-click the lock icon at the upper right corner of the graph window which contains the fitted curve.
Choose "Change Parameters" flyout. It reopen the NLFit tool.
2) If you want to change the parameter values, select the "Parameters" tab in the tool, double-click the value to enter
the new value you like.
3) If you don't want to let Origin fit further with the given parameter set, but just want to update the curve accordingly,
you can press Chi-Square button, and "Done" button to close the tool.
If you like to start fitting again from the given parameter set as new initials, you can press either "Fit until converged"
button, or the "Fit" button to fit and close the tool.
This process is also convenient and useful way to find a goof initial parameter values,
especially for the user-defined functions which typically don't come with the parameter initialization routines.
Hope this helps you.
--Hideo Fujii
OriginLab |
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Where is the y=a/x function?