Subset data.frame Rows.R

`[[.data.frame` <- function(x,...,exact=TRUE) {
  na <- nargs() - !missing(exact)
  if (!all(names(sys.call()) %in% c("", "exact"))) 
    warning("named arguments other than 'exact' are discouraged")
  if (na < 3L)
  {
    (function(x, i, exact)
    {
      if (is.matrix(i))
      {
        as.matrix(x)[[i]] 
      } else {
          .subset2(x, i, exact = exact)
      })(x, ..., exact = exact)
  } else if(missing(..2)){
    as.matrix(x)[..1,] 
  } else{
    col <- .subset2(x, ..2, exact = exact)
    i <- if (is.character(..1))
          {
            pmatch(..1, row.names(x), duplicates.ok = TRUE)
          } else {
            ..1
          }
    col[[i, exact = exact]]
  }
}