R/ICCbareF.r

In ICC: Functions facilitating the estimation of the Intraclass Correlation Coefficient

ICCbareF<-function(x, y, data){
  ICCcall <- Call <-match.call()
  xc<-as.character(ICCcall[[2L]])
  yc<-as.character(ICCcall[[3L]])
  tdata<-data.frame(data[yc], data[xc])
  if(!is.factor(tdata[,2])){
    warning("x has been coerced to a factor")
    tdata[,2]<-as.factor(tdata[,2])
    }  
  tmp1<-aggregate(tdata[,1], list(tdata[,2]),FUN=mean)
  tmp2<-aggregate(tdata[,1], list(tdata[,2]), FUN=length)
  ord.data<-tdata[order(tdata[,2]),]
  Treat.m<-rep(tmp1$x,tmp2$x)
  Among<-(Treat.m-rep(mean(tdata[,1]),nrow(tdata)))^2
  Within<-(ord.data[,1]-Treat.m)^2
  MS<-(c(sum(Among),sum(Within)))/(c(length(tmp2$x)-1, length(tmp2$x)*(tmp2$x[1]-1)))
  var.a<-(MS[1]-MS[2])/tmp2$x[1]
list(ICC=var.a/(var.a+MS[2]))
}