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Hello!
I am a relatively new user of Splus. Upon
reading online manuals of Nonlinear Mixed Effects Model
(NLME) & na.include, I am still not sure
what exactly splus does when you include
na.action="">
in the model statement. The model
statement is attached below.
Questions: (1) Does Splus do the imputation
automatically for all the NAs for all variables? If so,
with what value - mean or median?
(2) what does it mean by adding a
level? (online manual of na.include). Many of the variables in my
dataset
are continuous variables.
(3) am I using the option na.include
incorrectly?
Any help in explaining this is greatly appreciated. I am
using SPLUS4, rel.3 on winNT, analyzing a longitudinal
data set with many of the timed visits have NAs; NLME with
4-parameter GOMPERTZ function.
Model Statement:
nlme(BMI ~ BMI.FUNC(A,B,C,D,AGE), fixed=list(A~., B~., C~.,
D~.),
random=list(A~., B~.), cluster=~ID,
start=list(fixed=c(16.71, 2.08, 2.33, -0.34)),
na.action="">,
control=list(tolerance=0.0001, pnls.tolerance=0.001,
lme.tolerance=0.000001),
data="" verbose=T)
Thank you in advance, W. Hlaing, University of South Florida,
Tampa, FL
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