r - 如何在 excel 中复制或复制 "fill"值向上或向下一定行数

Question

我不知道如何简单地将 data.frame 值按整数向上或向下复制。

例如，如果我有这个 data.frame df:

randcol <- c("s","a","m","p","l", "e","d","a","t","a","h","e","l","l","o")
x <- c(NA,NA,"a",NA,NA,NA,NA,"b",NA,NA,NA,"c",NA,NA,NA)
df <- data.frame(randcol, x)

我不知道如何mutate() df$x 并将每个字符复制/填充到2 行，以实现这个新的 df:

有哪些好的方法？有没有dplyr方式？

谢谢。戴夫

Answer 1

我们使用“x”中的非 NA 值创建一个分组变量，然后执行replacement

library(dplyr)
df %>%
   group_by(grp = cumsum(!is.na(x))) %>% 
   mutate(x = replace(x, 2:pmin(3,n()), x[1])) %>% 
   ungroup %>% 
   select(-grp)
# A tibble: 15 x 2
#   randcol x     
#   <fctr>  <fctr>
# 1 s       <NA>  
# 2 a       <NA>  
# 3 m       a     
# 4 p       a     
# 5 l       a     
# 6 e       <NA>  
# 7 d       <NA>  
# 8 a       b     
# 9 t       b     
#10 a       b     
#11 h       <NA>  
#12 e       c     
#13 l       c     
#14 l       c     
#15 o       <NA>  

---

或者另一种选择是先进行填充，然后在按'x'分组后将大于3的行号替换为NA

df %>%
   tidyr::fill(x) %>% 
   group_by(x1 = x) %>% 
   mutate(x = case_when(row_number() >3 ~ NA_character_,
                      TRUE ~ as.character(x))) %>%
   ungroup %>% 
   select(-x1)