Hi, I am trying to get 95% CI s around a quantile growth curve, but
my result looks strange to me.
Here is the function I defined myself
boot.qregress<-function(mat1, group, quantile, int, seed.1){
boot.fit<-NULL
set.seed(seed.1)
for (i in 1:int){
index<-sample((unique(mat1$Subject[mat1$Group==group])), length
(unique(mat1$Subject[mat1$Group==group])), replace=TRUE)
#make the bootstrapping dataset
mat.junk<-NULL
for (j in 1: length(index)){
mat.junk<-rbind(mat.junk, mat1[mat1$Subject==index[j], ])
}
boot.fit<-cbind(boot.fit, cobs(mat.junk$Day, mat.junk$Weight,
constraint="none", degree=2, tau=quantile, lambda=-1)$fitted)
}
boot.fit
}
The curves I made from the bootstrapping is attached, I don't
understand why for a group, the 5% curve drops suddenly around time
130. I am thinking about missingness since before 130 there are 50
patients, but after day 130 there are only 40 patients for this group.
Any suggestions on the R-code (especially about how to do the
bootstrapping for the growth curves) or why the drops happened would
be appreciated.
Thanks a lot,
Suyan

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