Solving Exponential equation with data

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Dear sir,
I want to find four unknowns(a,b,c,d) which would fit with the model as y = a*(1-exp(-b*x)) + c*(exp(d*x)-1).
I am attaching data herewith. Please help me in chosing initial guess for unknowns.
Please provide steps and code in case for me to get started and able to fit it with the model.
Thank you
  2 Comments
Onkar Khadke
Onkar Khadke on 11 Sep 2020
Can you tell me how did you got those a b c d values? If you have used any code then please share it, it will help me as I have to fit many other data points.

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Accepted Answer

Alan Stevens
Alan Stevens on 10 Sep 2020
Try
a = 0.0093; b = 0.0095; c = 0.0035; d = 0.00185;
f = a*(1 - exp(-b*x)) + c*(exp(d*x) - 1);
plot(x,y,'o',x,f),grid
xlabel('x'),ylabel('y')
legend('data','function')
to get
However, the curve fitting toolbox shoud get an even better fit (I don't have the curve fitting toolbox, so did a rough fit outside of Matlab).
  3 Comments
Onkar Khadke
Onkar Khadke on 11 Sep 2020
Alright. I am Thankful for the help.

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