Date: Dec 10, 2012 7:55 AM Author: ariel Subject: Re: fitting ( cftool ) actually it does say something :

"Fit computation did not converge:

Fitting stopped because the number of iterations or function evaluations exceeded the specified maximum."

and :

"Warning: A negative R-square is possible if the model does not contain a constant term and the fit is poor (worse than just fitting the mean). Try changing the model or using a different StartPoint."

which says nothig to me.