loops

Hi R friends,
[...]
 
cra <- function(x) {
  nc <- dim(x)[2]
  nr <- dim(x)[1]

  ca <- apply(x,2,mean)
  xc1 <- t(x)-ca
  xc <- t(xc1)
  xr1 <- apply(xc,1,rank)
  xr <- t(xr1)

  s <- NULL
  k <- 0
  for ( j in 1:(nc-1)) {
    for (jp in (j+1):nc ) {
      k <- k+1
      s[k] <- a1(xr[,j],xr[,jp])
     }
   }
  cra <- max(s)
}

a1 <- function(x,y){
  nr <- length(x)
  h <- x-y
  s <- 0
  for( i in 1:(nr-1)){
    ip <- (i+1):nr
    a <- h[i]-h[ip]
    s<- s+sum(a*a)
  }
  return(s)
}

OK. I have had a look to a1(.).
You can remove the loop on this way (only code improved, did not thougth
about the real problem...):

a1 <- function(x,y){
  nr1 <- length(x) - 1
  h <- x - y
  return(sum((h[rep(1:nr1, nr1:1)] - h[nr1 - sequence(nr1:1) + 2])^2))
}

## So it should not be necessary to have an own function a1(.), and
cra(.) looks as follows:


cra <- function(x) {
  nr1 <- dim(x)[1] - 1
  nc <- dim(x)[2]
  xr <- t(apply(t(t(x) - apply(x, 2, mean)), 1, rank))
  ## Not readable any more, but also not so many variables in use.
  ## Maybe this can be simplified ???
  s <- NULL
  k <- 0
  for ( j in 1:(nc - 1)) {
    for (jp in (j + 1):nc ) {
      k <- k + 1
      h <- xr[ ,j] - xr[ ,jp]
      s[k] <- sum((h[rep(1:nr1, nr1:1)] - h[nr1 - sequence(nr1:1) +
2])^2)
     }
   }
  cra <- max(s) 
## or do you want return(max(s)) ???
}


Maybe you can remove some more loops, but there's no more time left ....

Regards,
Uwe Ligges
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