Dear colleagues, I wan to to adjust the Von Bertalanffy model TLLinf*(1-exp(-K*(AGE-t0)) to is fish length (TL) and age (AGE) . Linf, K and t0 are parameters of the model. The growth of the species I have been working seems to differ between sexes I would like to know how to get simultaneous ML estimates: i) of the three parameters discriminated by sex; ii) of a common parameter and the two other discriminated by sex. using the overall data set which includes a factor variable with two levels Regards, Ivone Figueiredo [[alternative HTML version deleted]]