Dear All, I tried to fit Lloyd-Taylor function for soil respiration data, but convergence is often failed and even if the model converged there is extremely high uncertainty in parameter estimates. The fitted model is: y=a-b/(x-c), where a, b, and c are the parameters. (Note that it is not the original Lloyd-Taylor function, in my version the dependent variable is the logarithm of respiration). I have already recognized the origin of the problem: since c<min(x), partial derivatives of y with respect to b and c are highly correlated. I suppose that it can be solved by an appropriate re-parametrization, but I was not able to find it. Could you suggest an appropriate re-parametrization? Thanks Zoltan
Botta-Duk?t Zolt?n -------------------------------- ?kol?giai ?s Botanikai Int?zet Magyar Tudom?nyos Akad?mia ?kol?giai Kutat?k?zpont -------------------------------- 2163. V?cr?t?t, Alkotm?ny u. 2-4. tel: +36 28 360122/157 fax: +36 28 360110 botta-dukat.zoltan at okologia.mta.hu www.okologia.mta.hu Zolt?n BOTTA-Duk?t -------------------------------- Institute of Ecology and Botany Hungarian Academy of Sciences Centre for Ecological Research -------------------------------- H-2163 V?cr?t?t, Alkom?ny u. 2-4. HUNGARY Phone: +36 28 360122/157 Fax..: +36 28 360110 botta-dukat.zoltan at okologia.mta.hu www.okologia.mta.hu