library(tidyverse)
df <- tibble(X = c("A1", "A2", "A3", "A4", "A5", "A5", "A6", "A7", "A8", "A8", "A9", "A9"),
             Y = c(31, 52, 45, 86, NA, 50, 93, 85, 59, NA, 85, NA),
             Z = c(70, 64, 51, 38, 18, NA, 76, 54, NA, 69, NA, 96),
             D = c(1,1,1,1,2,2,1,1,2,2,2,2))
> df
# A tibble: 12 x 4
   X         Y     Z     D
   <chr> <dbl> <dbl> <dbl>
 1 A1       31    70     1
 2 A2       52    64     1
 3 A3       45    51     1
 4 A4       86    38     1
 5 A5       NA    18     2
 6 A5       50    NA     2
 7 A6       93    76     1
 8 A7       85    54     1
 9 A8       59    NA     2
10 A8       NA    69     2
11 A9       85    NA     2
12 A9       NA    96     2

列X具有重复值，有时重复两次。列D正在测量这些值的出现次数。列Y和Z具有一些得分。我希望这些得分在列X内的重复观测中重复。我尝试使用fill()方法，输出如下所示

df %>%
  filter(D == 1) %>%
  bind_rows(df %>%
              filter(D != 1) %>%
              fill(c("Y", "Z"), .direction = "downup")
  )

# A tibble: 12 x 4
   X         Y     Z     D
   <chr> <dbl> <dbl> <dbl>
 1 A1       31    70     1
 2 A2       52    64     1
 3 A3       45    51     1
 4 A4       86    38     1
 5 A6       93    76     1
 6 A7       85    54     1
 7 A5       50    18     2
 8 A5       50    18     2
 9 A8       59    18     2
10 A8       59    69     2
11 A9       85    69     2
12 A9       85    96     2

然而，无论我使用什么.direction选项，我似乎都不能得到正确的数字。例如，在上面的输出中，对于A9，Z应该重复96两次。A8也有同样的问题。
我想要的输出如下

X         Y     Z     D
   <chr> <dbl> <dbl> <dbl>
 1 A1       31    70     1
 2 A2       52    64     1
 3 A3       45    51     1
 4 A4       86    38     1
 5 A6       93    76     1
 6 A7       85    54     1
 7 A5       50    18     2
 8 A5       50    18     2
 9 A8       59    69     2
10 A8       59    69     2
11 A9       85    96     2
12 A9       85    96     2