| T O P I C R E V I E W |
| 99originProblems |
Posted - 02/26/2014 : 6:45:42 PM
I can't get my user defined function to work.
I linearized a rising exponential function
V=V0(1-e^(-t/T1))
to get
ln(1-(V/V0))=-(t/T1)
I have data from V and t in Origin.
ind. variables: t
dep. variable: V
parameters: V0, T1
Function: ln(1-(V/V0))=-(t/T1)
What am I doing wrong? |
| 1 L A T E S T R E P L I E S (Newest First) |
| Kathy_Wang |
Posted - 02/27/2014 : 03:14:25 AM
Hi,
The function ln(1-(V/V0))=-(t/T1) is an implicit function, so it must be created as an implicit function (i.e. Function Model set to Implicit) and also you need to use the Orthogonal Distance Regression iteration algorithm. You may refer to this tutorial to learn how to carry out implicit fit (Requires OriginPro 9.0 or above).
However, you could actually directly carry out nonlinear curve fit with the exponential function V=V0(1-e^(-t/T1)), in that case you may refer to this tutorial.
In addition, if you actually want to carry out linear fit for your data, you might need to first calculate the value of ln(1-(V/V0)) from V and use this as the dependent variable for linear fit. You may use the Set Column Values tool to calculate the new dependent variable, you could also refer to this tutorial to see how to set column values using another column.
Kathy
Originlab |
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