>  # jacktest.r                 December 2007
>  #
>  # compare speeds for jackknife
>  #
>  # First method -- create matrix and use apply
>  # data
>   set.seed(5151917)
>   N <- 1000
>   v <- -log(runif(N))         # generate exponential RVs
>   mean(v,trim=.2)             # compute statistic on data
[1] 0.775349
>  # 
>   proc.time()       # read clock before execution
[1] 0.93 0.11 1.04 0.00 0.00
>   V <- matrix(v,N-1,N)
>  # compute statistic
>   vps <- apply(V,2,mean,trim=.2)
>   proc.time()       # read clock after execution
[1] 2.30 0.18 2.47 0.00 0.00
>   var(vps)
[1] 8.235568e-07
>   mean(vps)
[1] 0.7756938
>  #
>  # Second method -- using loop
>   proc.time()       # read clock before execution
[1] 2.30 0.18 2.47 0.00 0.00
>   vps <- rep(0,N)
>   for(i in(1:N)){ vps[i]<-mean(v[-i],trim=.2) }
>   proc.time()       # read clock after execution
[1] 3.19 0.18 3.37 0.00 0.00
>   mean(vps)
[1] 0.7756938
>   var(vps)
[1] 8.235568e-07
>  # done
>   rm(list=ls())
>  q()