在完全误解了问题之后，这是我的最终答案：

After completely misunderstanding the question, here is my final answer:

# named after beetroot for being the first to ever need this functionality
beetroot <- function(x) {
    # count NA
    num.na <- sum(is.na(x))
    # remove NA
    x <- x[!is.na(x)]
    # glue the number of NAs at the end
    x <- c(x, rep(NA, num.na))
    return(x)
}

# apply beetroot over each column in the dataframe
as.data.frame(lapply(df, beetroot))

它将对NA进行计数，删除NA，并在每个列的底部粘贴NA数据框。

It will count the NAs, remove the NAs, and glue NAs at the bottom for each column in the data frame.