On Aug 26, 2012, at 5:06 PM, Jinsong Zhao wrote:

Hi there,

In my code, there is a for loop like the following:

  pmatrix <- matrix(NA, nrow = 99, ncol = 10000)
  qmatrix <- matrix(NA, nrow = 99, ncol = 3)
  paf <- seq(0.01, 0.99, 0.01)
  for (i in 1:10000) {
      p.r.1 <- rnorm(1000, 1, 0.5)
      p.r.2 <- rnorm(1000, 2, 1.5)
      p.r.3 <- rnorm(1000, 3, 1)
      pmatrix[,i] <- quantile(c(p.r.1, p.r.2, p.r.3), paf)
  }
  for (i in 1:99) {
     qmatrix[i,] <- quantile(pmatrix[i,], c(0.05, 0.5, 0.95))
  }

Because of the number of loop is very large, e.g., 10000 here, the code is very slow.

I would think that picking the seq(0.01, 0.99, 0.01) items in the first case and the 500th, 5000th and the 9500th in the second case, rather than asking for what `quantile` would calculate, would surely be more "statistical", in the sense of choose order statistics anyway. Likely much faster.

--
David.


Is it possible to optimize the code?

Any suggestion will be greatly appreciated.

Regards,
Jinsong

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