Hello, For my master thesis I have fitted an individual tree diameter growth model and a survival probability model separately using R, but I was told that simultaneous estimation of these two models would minimize overall errors and provide a variance-covariance matrix as a whole. In that respect, can you please tell me if I can do it with nlssystemfit using SUR (seemingly unrelated regression) method? If not, do you know how can I do it in R? My equations are: - tree diameter growth model d_richards_k<-d2~A*(1-exp(-(k0+k1*puro+k2*GL1/100+k3*1/G1+k4*Tmedmax/100+k5* Perc_G_ec1))*(1-(d1/A)^(1-m)))^(1/(1-m)) nls_d_richards_k<-nlsLM(d_richards_k,start=list(A=100,k0=0.6,k1=0,k2=0,k3=0, k4=0,k5=0,m=0.6),control=nls.lm.control(maxiter=500)) - survival probability model mortal_final<-glm(sobrev~Verao+alto_fuste:puro+IC1arv+G1+Perc_G_ec1,family=b inomial) Thank you! Best regards, Francisco Goes [[alternative HTML version deleted]]