Dear R users, I?m using the constrOptim.nl<http://constrOptim.nl> to carry out non-linear fit with constraints between experimental and modelled data. As far as I understand the parameter ?fval" indicates the goodness of this fit. My first question is: Is the fval parameter similar to commonly used chi^2 parameter? Second: if you?d need to decide which set of models best fit your experimental data by comparing the different fval values obtained, how can you use R to determine if the differences between fval values is statistically significant? I?d appreciate your feedback. Regards. Juan C. Munoz-Garc?a [[alternative HTML version deleted]]