Exponential cooling down curve fitting

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aalok
aalok 2015-5-15
HEllo,
I have the curve which is essentially a cooling down measurement for a device. I know the equation to be fitted to this curve which is as under:
f(x) = (1236*((r1*exp(-x/t1))+(r2*exp(-x/t2))+(r3*exp(-x/t3))+(r4*exp(-x/t4)
)))+(((37.08*(r9*exp(-x/t9))+(r10*exp(-x/t10)))/(((r9*exp(-
x/t9))+(r10*exp(-x/t10))+(r5*exp(-x/t5))+(r6*exp(-x/t6)
)+(r7*exp(-x/t7))+(r8*exp(-x/t8)))))*((32.33*((r5*exp(-
x/t5))+(r6*exp(-x/t6))+(r7*exp(-x/t7))+(r8*exp(-x/t8)
)))-((r9*exp(-x/t9))+(r10*exp(-x/t10)))))
The probem is following:
I fit this custom equation in curve fitting GUI, and set the values asshown in attachment ('curve_fitting_options.jpg')
It yield good fitting with the warning that, *Fit computation did not converge: Fitting stopped because the number of iterations or function evaluations exceeded the specified maximum.
Fit found when optimization terminated:*
I am also attaching the obtained unknown parameters from curve fitting ('Curve_fitting_Result.jpg') and also attaching Curve fitting image ('Curve_fitting_image.jpg').
Can you tell me is it a good fit or not because sometimes the fit depends highly on my starting point . Whatever starting point set by MATLAB by default doesnot give good fitting to me so I change some of them and then it gave me this result. Can I rely on this result? Is there any other way to get perfect result ?
Thank you very much.

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