r - 将NA移到数据框中每一列的末尾

Question

我有这样一个数据框:

df <- structure(list(a = c(NA, NA, 1L, 2L, 3L, 4L, 5L, 6L, 7L, 8L), b = c(NA, NA, NA, 1L, 2L, 3L, 4L, 5L, 6L, 7L), d = c(NA, NA, NA, NA, 1L, 2L, 3L, 4L, 5L, 6L)), .Names = c("a", "b", "d"), row.names = c(NA, -10L), class = "data.frame")

> df
    a  b  d
1  NA NA NA
2  NA NA NA
3   1 NA NA
4   2  1 NA
5   3  2  1
6   4  3  2
7   5  4  3
8   6  5  4
9   7  6  5
10  8  7  6

在每列中，我想将非 NA值向上移动，并将 NA移至末尾:

> df.out
    a  b  d
1   1  1  1
2   2  2  2
3   3  3  3
4   4  4  4
5   5  5  5
6   6  6  6
7   7  7 NA
8   8 NA NA
9  NA NA NA
10 NA NA NA

更新以使我的问题更清楚..

df <- structure(list(a = c(NA, NA, 1, 5, 34, 7, 3, 5, 8, 4), b = c(NA, 
NA, NA, 57, 2, 7, 9, 5, 12, 100), d = c(NA, NA, NA, NA, 5, 7, 
2, 8, 2, 5)), .Names = c("a", "b", "d"), row.names = c(NA, -10L
), class = "data.frame")

> df
    a   b  d
1  NA  NA NA
2  NA  NA NA
3   1  NA NA
4   5  57 NA
5  34   2  5
6   7   7  7
7   3   9  2
8   5   5  8
9   8  12  2
10  4 100  5

应导致:

    a   b  d
1   1  57  5
2   5   2  7
3  34   7  2
4   7   9  8
5   3   5  2
6   5  12  5
7   8 100 NA
8   4  NA NA
9  NA  NA NA
10 NA  NA NA

似乎是一项简单的任务，但我被困在从何开始。您能帮上忙吗？

Answer 1

在完全误解了问题之后，这是我的最终答案:

# 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，并在数据帧中的每一列的底部粘贴NA。