All,
I've solved part of the problem below by making sure that the formula in
the grouped data object is the same as the formula specified within lme
(this isn't the case in the cited example from Pinheiro & Bates).
However, augPred seems to plot only a linear model instead of the
polynomial model. Does anyone know how to make sure that augPred plots
the same model as that specified in the model (as below)?
cheers,
dave
________________________________
From: Afshartous, David
Sent: Thursday, September 07, 2006 6:18 PM
To: r-help@stat.math.ethz.ch
Cc: Afshartous, David
Subject: augPred plot in nlme library
All,
I'm trying to create an augPred plot in the nlme library, similar to the
plot on
p.43 of Pinheiro & Bates (Mixed Effects Models in S and S-Plus) for
their Pixel data.
My data structure is the same as the example but I still get the error
msg below.
> comp.adj.UKV <- groupedData(adj.UKV ~ Time | Patient_no/Lisinopril,
data = comp.adj.UKV.frm, order.groups = F)
> fm1comp = lme(adj.UKV ~ Time + Time.sq, data = comp.adj.UKV, random =
list(Patient_no = ~ 1) )
> plot(augPred(fm1comp, level= 1))
Error in model.frame(formula, rownames, variables, varnames, extras,
extranames, :
variable lengths differ
I've checked all the variale lengths, and have also made sure that
factors are correctly defined
as factors. Is there anything special I need to be doing for augPred
to work correctly? I checked
the help but didn't find much.
cheers,
dave
David Afshartous, PhD
University of Miami
School of Business
Rm KE-408
Coral Gables, FL 33124
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