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

[sneaffer]

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

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