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...are wildly off. Or am I doing something daft? Milk yield for five cows is measured weekly for 45 weeks. Yield is simulated as cubic function of weekno + random cow effect (on intercept) + residual error. I want to recover an estimate of the fixed curve. ############### library(nlme) set.seed(1) ncows <- 5; nweeks <- 45; week <- 1:nweeks mcurve <- 25 + 0.819*week - 0.0588*week^2 + 0.000686*week^3 cow.eff <- rnorm(ncows) week <- rep(week, ncows) cow <- gl(ncows,nweeks) yield <- mcurve + cow.eff[cow] + rnorm(ncows*nweeks) lmefit <- lme(yield ~ poly(week,3), random = ~1...