Curve fitting tool error with custom equation

Hi,

I'm trying to fit this equation a*exp(-b*x) + c*(1/x)+d to my data. Using the curve fitting tool I constantly get this error:

Inf computed by model function, fitting cannot continue.

Try using or tightening upper and lower bounds on coefficients.

Yes, I tried to tighten the bounds on coefficients but it didn't really work.

You can find attached a .mat file with my data.

Here's a screenshot:

Thank you so much!!

Answer 1

[Steven Lord]

Does your data contain a point with x = 0? If so the term c*(1/x) is going to give you Inf or NaN (depending on whether or not c is 0 when you try to evaluate the fit) and the Curve Fitting Tool does not support that.

If you want to keep that form, remove data points with x = 0 from your data before trying to fit.

[Luca Fanciullini]

Solved, thank you so much!