# [R] nlsystemfit help

Francisco Goes francisco.goes at celpa.pt
Fri Aug 29 16:11:30 CEST 2014

```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

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