| T O P I C R E V I E W |
| Sam__Perry |
Posted - 03/18/2014 : 08:49:47 AM
I have the following function that I am using to model some experimental data
y = pi^1/2 * x * exp(x^2) * erfc(x)
I have a column of y values that I determined experimentally, and want to use this model to generate a column of x values to go with each data point. I cannot work out a simple way to do this mathematically due to the combination of exp and erfc functions. Is there a work around?
Many thanks!
Origin Ver. and Service Release (Select Help-->About Origin): 9.1.0
Operating System: Windows 7 |
| 1 L A T E S T R E P L I E S (Newest First) |
| Hideo Fujii |
Posted - 03/18/2014 : 4:13:42 PM
Hi Sam,
Though this is a bit cumbersome way, you may try it:
1) Using Fitting Function Builder, define your function, say f(x)=experfc(x), with a parameter "p" instead of the constant pi.
2) Make the function plot of your function. ("File: New: Function Plot: 2D Function Plot")
3) Double-click the function plot to show Plot Details, and press "Workbook" button to make the data sheet.
4) Highlight the Y column, and start NLFit ("Analysis: Fitting: Nonlinear Curve Fit").
5) In NLFit, select your function, and in the left panel, select "Find X/Y" tab, and turn ON the "Find X from Y" check box. Click Fit to finish fitting. (Of course, it converges with pi.)
6) You find a new sheet"FitNLFindXfromY1" in the worksheet. Now, you can copy your Y values to the first column in this sheet, and you get the corresponding Xs.
Hope this helps.
--Hideo Fujii
OriginLab
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P.S.
I have noticed after I made a function plot of your function that it is a monotonically increasing function.
Therefore, it is safe to switch the positions and the designations (X and Y) of the first and second columns;
Then you can run "Analysis: Mathematics: Interpolate/Extrapolate Y from X" to get the actual Xs.
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