Greetings:
I am having problems with time-varying individual covariate names when using unequal time intervals in the Huggins robust design. When I use a 1 for the time intervals all works fine, but when I change to unequal time intervals I get an error message (see below) and the design matrix is not what I want. The relevant parts of the code are followed by the error message and design matrix.
Is there some trick to using individual covariates with unequal time intervals? I read there is an older method of naming individual covariates – do I need to figure that out and use?
You can see I tried time.varying for the design matrix, but it worked the same as if I skipped that step.
Thanks for any advice. Cheers, Mary
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intervals = c(0,0.67,0,0,0,0.67,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0,1,0,0,0)
…
reg.rob.prevcap.processed=process.data(HCBT.robust.data,begin.time=1,model="RDHuggins",time.intervals=intervals)
design.p=list(time.varying=c("prevcap"))
design.parameters=list(p=design.p)
reg.rob.prevcap.ddl=make.design.data(reg.rob.prevcap.processed,parameter=design.parameters)
…
p.prevcap=list(formula=~prevcap)
reg.mod.wIC<-mark(reg.rob.prevcap.processed,reg.rob.prevcap.ddl,
model.parameters=list(S=Sdot, p=p.prevcap, c=cdot, GammaDblPrime=GammaDblPrime.0,
GammaPrime=GammaPrimedot),output=F,silent=T,filename=paste("WIC",sep=""))
Error message upon running model
The following covariates are missing: prevcap1.67
The following covariates are missing: prevcap2.34
The following covariates are missing: prevcap3.34
The following covariates are missing: prevcap4.34
The following covariates are missing: prevcap5.34
The following covariates are missing: prevcap6.34
The following covariates are missing: prevcap7.34
The following covariates are missing: prevcap8.34
The following covariates are missing: prevcap9.34
If any are used in the resulting model it will fail
Desing matrix
> reg.mod.wIC$design.matrix
S:(Intercept) p:(Intercept) p:prevcap c:(Intercept)
S g1 c1 a0 t1 "1" "0" "0" "0"
p g1 s1 t1 "0" "1" "prevcap1" "0"
p g1 s1.67 t1 "0" "1" "prevcap1.67" "0"
p g1 s2.34 t1 "0" "1" "prevcap2.34" "0"
p g1 s3.34 t1 "0" "1" "prevcap3.34" "0"
p g1 s4.34 t1 "0" "1" "prevcap4.34" "0"
p g1 s5.34 t1 "0" "1" "prevcap5.34" "0"
p g1 s6.34 t1 "0" "1" "prevcap6.34" "0"
p g1 s7.34 t1 "0" "1" "prevcap7.34" "0"
p g1 s8.34 t1 "0" "1" "prevcap8.34" "0"
p g1 s9.34 t1 "0" "1" "prevcap9.34" "0"
c g1 s1 t2 "0" "0" "0" "1"
Gamma'' g1 c1 a0 t1 "0" "0" "0" "0"
Gamma' g1 c1 a0.67 t1.67 "0" "0" "0" "0"