fitting a*(1-exp(-b*x))

Hello,

I have been trying to fit a few datasets with a function of the type:

a*(1-exp(-b*x)),

or

a*exp(-b*x)+c

which has proved usually quite unsuccessful. I have tried from the Curve Fitting Toolbox, as well as directly from the code. I have played with the starting points, and the TolFun and TolX parameters. The fit from Matlab is either totally off, or just returns the initial values.

Would someone be able to explain what is the best way to fit with this kind of model.

Thanks,

Raphael

[Star Strider]

Post your code and at least one of your representative data sets.