当某些键有多个值时,使用tidyr::pivot_

df <- data.frame(ColA=c("A", "B", "B", "C"), ColB=letters[23:26])

  ColA ColB
1    A    w
2    B    x
3    B    y
4    C    z

  ColA ColB
1    A    w
2    B    xy
3    C    z

常客 pivot_wider() 将引发警告并将值转换为列表:

df.wide <- df %>%
    pivot_wider(names_from=ColA, values_from=ColB)

Warning message:
Values are not uniquely identified; output will contain list-cols.
* Use `values_fn = list` to suppress this warning.
* Use `values_fn = length` to identify where the duplicates arise
* Use `values_fn = {summary_fun}` to summarise duplicates 

# A tibble: 1 x 3
  A         B         C        
  <list>    <list>    <list>   
1 <chr [1]> <chr [2]> <chr [1]>

根据警告,它看起来像 支点() value_fn() 类似于我想要的中间步骤:

# intermediate step
df.wide <- df %>%
    pivot_wider(names_from=ColA, values_from=ColB, values_fn=SOMETHING)

   A  B  C
1  w  xy z

values_fn() 只接受摘要函数,而不是处理字符数据的函数(如 paste() )

我能得到的最接近的结果是:

df %>%
  pivot_wider(names_from=ColA, values_from=ColB, values_fn=list) %>% 
  mutate(across(everything(), as.character)) %>%
  pivot_longer(cols=everything(), names_to="ColA", values_to="ColB")

# A tibble: 3 x 2
  ColA  ColB             
  <chr> <chr>            
1 A     "w"              
2 B     "c(\"x\", \"y\")"
3 C     "z" 

带着额外的变异 gsub() -类型函数。当然还有更简单的方法!最好在 tidyverse ,但也对其他软件包开放。

谢谢