R/resample.R

In warnes/gdata: Various R Programming Tools for Data Manipulation

## The base R 'sample' function behaves differently if it is passed a
## sampling vector of length 1 than if it is passed a
## vector of length greater than 1.  For the 1-element
## case it samples from the list 1:x, instead of from the contents
## of x.  This function remove the special case: it always samples from
## the provided argument, no matter the length.

resample <- function(x, size, replace = FALSE, prob = NULL)
{
  if(length(x)<1)
  {
    if(!missing(size) && size>0)
      stop("Requested sample of size ", size, " from list of length 0")
    else
      x[FALSE]
  }
  else if(length(x)==1)
  {
    if(missing(size) || size==1)
      x
    else if(size>=1 && replace==TRUE)
      rep(x, size)
    else if(size < 1)
      x[FALSE]
    else
      stop("cannot cannot take a sample larger than the population",
           " when 'replace = FALSE'")
  }
  else
  {
    sample(x, size, replace, prob)
  }
}