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Hello, I am trying to fit a nonlinear model of the form of: A*x^b*exp(-c*x) This represents a lactation curve. I have a bunch of cows, so I want COW to be a random effect. I have been trying the following code with very littel success: > fm1 <- nlme(yield ~ A*(DIM^B)*(exp(-C*DIM)), + data = group, + fixed = A + B + C ~ 1, + start = c(A = 20, B =

Do you send information about lactation curve analyse with no linear mixed model, with fixed effects (herd, year season, parity) and random effects (cow)?. Than you very much Mario Fernando [[alternative HTML version deleted]]

Hello, I try to do a very simple nonlinear regression. The function is y = (b0 + b1*x1 + b2*x2 + b3*x3) * x4^b4 I think I do everything well, but as I set the starting value of b4 to 0 (it is the theoretically sane starting value), it converges very quickly, and to the wrong solution. Wrong in a sense, that 1) we do not expect this and 2) we do not get this on E-Views, Stata and SAS. I do not