R/qint.R

In musto101/wilcox_R: What the package does (short line)

qint <-
function(x,q=.5,alpha=.05,pr=FALSE){
#
# Compute a 1-alpha confidence interval for the qth quantile
# The function returns the exact probability coverage.
#
if(pr){
if(sum(duplicated(x)>0))print("Duplicate values detected; use hdpb")
}
n<-length(x)
ii<-floor(q*n+.5)
jj<-ii+1
if(ii<=0)stop("Cannot compute a confidence interval for this q")
if(jj>n)stop("Cannot compute a confidence interval for this q")
jjm<-jj-1
iim<-ii-1
cicov<-pbinom(jjm,n,q)-pbinom(iim,n,q)
while(cicov<1-alpha){
iim<-max(iim-1,0)
jjm<-min(jjm+1,n)
if(iim==0 && jjm==n)break
cicov<-pbinom(jjm,n,q)-pbinom(iim,n,q)
}
xsort<-sort(x)
low<-xsort[iim+1]
hi<-xsort[jjm]
if(cicov<1-alpha){
if(pr)print("Warning: Desired probability coverage could not be achieved")
}
list(ci.low=low,ci.up=hi,ci.coverage=cicov)
}