Rhelpers:

#' Function merge data frames without loosing order of either X or Y frame
#' Shamelessly stolen from: https://www.r-statistics.com/2012/01/merging-two-data-frame-objects-while-preserving-the-rows-order/
#' @param x first data frame to merge
#' @param y second data frame to merge
#' @param by merge by single column
#' @param by.x merge by column in x
#' @param by.y merge by column in y
#' @param sort whether to sort the column (defaults to FALSE)
#' @param keep_order keep order in x (1) or y (2)

#' @return merged data frame

#' @export

merge.with.order <- function(x,y, ..., sort = F, keep_order)
{
  # this function works just like merge, only that it adds the option to return the merged data.frame ordered by x (1) or by y (2)
  add.id.column.to.data <- function(DATA)
  {
    data.frame(DATA, id... = seq_len(nrow(DATA)))
  }
  # add.id.column.to.data(data.frame(x = rnorm(5), x2 = rnorm(5)))
  order.by.id...and.remove.it <- function(DATA)
  {
    # gets in a data.frame with the "id..." column.  Orders by it and returns it
    if(!any(colnames(DATA)=="id...")) stop("The function order.by.id...and.remove.it only works with data.frame objects which includes the 'id...' order column")
    
    ss_r <- order(DATA$id...)
    ss_c <- colnames(DATA) != "id..."
    DATA[ss_r, ss_c]
  }
  
  # tmp <- function(x) x==1; 1	# why we must check what to do if it is missing or not...
  # tmp()
  
  if(!missing(keep_order))
  {
    if(keep_order == 1) return(order.by.id...and.remove.it(merge(x=add.id.column.to.data(x),y=y,..., sort = FALSE)))
    if(keep_order == 2) return(order.by.id...and.remove.it(merge(x=x,y=add.id.column.to.data(y),..., sort = FALSE)))
    # if you didn't get "return" by now - issue a warning.
    warning("The function merge.with.order only accepts NULL/1/2 values for the keep_order variable")
  } else {return(merge(x=x,y=y,..., sort = sort))}
}