I have a series of (x,y) data that should be fitted by an equation (In order to finding the equation parameters: A, D, T).
I used OriginPro software for curve fitting. In fitting tab, the software needs some initial values for parameters.
How these initial values must be determined?
Equation: y=A*exp(DT/(T-x))
Parameters: A, D, T
The datasheet are attached.
Did you try to supply random values? If you supply random values how much the final results differ?
Dear Ajit kumar Roy
I want find the parameter of the mentioned equation (A, D, T) and have not any idea about the min or max of the parameters. I just have "x" and "y" data.
Dear Todor Balabanov
Regarding the literature, I try some meaningful initial values but by the changing initial values the final parameters values will significantly differ
Start by 0.2 value and see how it goes. look at chi square and adjust the values accordingly. Iteration could also help.
Hi Reza Rashidi, are you trying to fit the four sets of data (fit.xlsx) with an exponential function?
Dear Yew-Chung Chak
I want to fit data with the mentioned equation ( y=A*exp(DT/(T-x)) ), and find the parameters (A, D, T).
Hi Reza Rashidi ,
From the model, "A*exp(D*T/(T - x))" (see Fig. 1) and the x data, you can guess the initial value of T (in the range of 650 ~ 750) that forms the vertical asymptote.
Yew-Chung Chak
Thanks for your help.
Do you fit the data with Matlab? may you give me the codes?
Hi Reza Rashidi, Since there are only 5 points in each data set, I used an interactive online curve fitting tool known as MyCurveFit. No special code is required. I just entered your exponential model in the User-Defined text field and provided some good starting point estimates on the parameters [a], [b], [c] in the model a*exp(b*c/(c - x)).
https://mycurvefit.com/
The graphs in the previous post are plotted using Octave Online.
https://octave-online.net/
In my experience, Origin will suggest its best fitting constants. You can modify them, but there is not a must to determine the constants A, D and T.
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