[R] use of covariates with nlmeODE

[Jesus Frias]

Dear R-helpers,
	I have some problem with a model I am trying to run with nlmeODE. I have a
covariate that I want to include in the model and I can't find in the
documentation how to include it in the model so that it can calculate it.

>formula(trial)

PME ~ time | Ident


abcnoniso <- list(DiffEq=list(
                    debdt = ~ -ksol*pH*eb ,
                    desdt = ~ ksolref*pH*eb-kdegref*pH*es,
                    dpHdt= ~ -k*(pH-pHinf)
                    ),
                  ObsEq=list(
                    c1 = ~ 0,
                    c2 = ~ es,
                    c3 = ~ 0),
                  Parms=c("ksol","kdeg","k","es0","eb0"),
                  States=c("es","eb","pH"),
                  Init=list("eb0","es0",3))
abcnonisomodc <- nlmeODE(abcnoniso,trial)

The variable pHinf is a covariate that changes from experiment to
experiment. The model does not take very well pHinf.

regards,

Jesus


--------------------------------------------------------------
Jesús María Frías Celayeta
School of Food Sci. and Env. Health.
Faculty of Tourism and Food
Dublin Institute of Technology
Cathal Brugha St., Dublin 1. Ireland
t +353 1 4024459 f +353 1 4024495
w www.dit.ie/DIT/tourismfood/science/staff/frias.html
--------------------------------------------------------------



-- 
This message has been scanned for content and 
viruses by the DIT Information Services MailScanner 
Service, and is believed to be clean.
http://www.dit.ie