[R] How to erase (replace) certain elements in the data.frame?

[Thomas Levine]

This should do the same thing

random.del <- function (x, n.keeprows, del.percent){
  del<-function(col){
    col[sample.int(length(col),length(col)*del.percent/100)]<-NA
    col
  }
  change<-n.keeprows:nrow(x)
  x[change,]<-lapply(x[change,],del)
  x
}

This is faster because it's vectorized.

[1] "Mine"
   user  system elapsed
  0.004   0.000   0.002
[1] "Yours"
   user  system elapsed
  1.172   0.020   1.193

Tom

On Sat, Apr 23, 2011 at 8:37 PM, sneaffer <sneaffer at mail.ru> wrote:
>
> Hello R-world,
> Please, help me to get round my little mess
> I have a data.frame in which I'd rather like some values to be NA for the
> future imputation process.
>
> I've come up with the following piece of code:
>
> random.del <- function (x, n.keeprows, del.percent){
>  n.items <- ncol(x)
>  k <- n.items*(del.percent/100)
>  x.del <- x
>  for (i in (n.keeprows+1):nrow(x)){
>    j <- sample(1:n.items, k)
>    x.del[i,j] <- NA
>  }
>  return (x.del)
> }
>
> The problems is that random.del turns out to be slow on huge samples.
> Is there any other more effective/charming way to do the same?
>
> Thanks,
> Sergey
>
> --
> View this message in context: http://r.789695.n4.nabble.com/How-to-erase-replace-certain-elements-in-the-data-frame-tp3470883p3470883.html
> Sent from the R help mailing list archive at Nabble.com.
>
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