R Under development (unstable) (2024-03-19 r86153 ucrt) -- "Unsuffered Consequences"
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> ## test use of replicates in svyby, svycontrast
> library(survey)
Loading required package: grid
Loading required package: Matrix
Loading required package: survival

Attaching package: 'survey'

The following object is masked from 'package:graphics':

    dotchart

> 
> data(api)
> dclus1<-svydesign(id=~dnum, weights=~pw, data=apiclus1, fpc=~fpc)
> rclus1<-as.svrepdesign(dclus1)
> 
> meanlogs_without<-svyby(~log(enroll),~stype,svymean, design=rclus1,covmat=TRUE)
> c_without<-svycontrast(meanlogs_without, quote(exp(E-H)))
> vcov(c_without)
           contrast
contrast 0.06862947
> 
> meanlogs_with<-svyby(~log(enroll),~stype,svymean, design=rclus1,covmat=TRUE,return.replicates=TRUE)
> 
> c_with<-svycontrast(meanlogs_with, quote(exp(E-H)))
> 
> v_with<- vcov(rclus1, c_with$replicates)
> 
> r<- attr(meanlogs_with, "replicates")
> vr_with<-vcov(rclus1,exp(r[,1]-r[,2]))
> 
> stopifnot(all.equal(as.numeric(v_with),as.numeric(vr_with)))
> stopifnot(all.equal(as.numeric(v_with),as.numeric(vcov(c_with))))
> 
> proc.time()
   user  system elapsed 
   1.51    0.28    1.78