为另一列中的每个唯一值向数据框添加新列

Question

I'd like to add a new column for each unique value in another column. Then for each of these columns the value will either be the value from the other column, or zero.

For the example below i would like to add 4 new columns (A:D), for column B would be (0,0,0,0,5,6,7,8,0,0,0,0,0,0,0,0) etc.

df <- data.frame(Group=rep(c('A', 'B', 'C', 'D'), each=4),
                 score=1:16)        
df

Answer 1

Using map_dfc :

library(purrr)
library(dplyr)
map_dfc(setNames(unique(df$Group), unique(df$Group)), 
        ~ ifelse(df$Group == .x, df$score, 0)) %>% 
  bind_cols(df, .)

   Group score A B  C  D
1      A     1 1 0  0  0
2      A     2 2 0  0  0
3      A     3 3 0  0  0
4      A     4 4 0  0  0
5      B     5 0 5  0  0
6      B     6 0 6  0  0
7      B     7 0 7  0  0
8      B     8 0 8  0  0
9      C     9 0 0  9  0
10     C    10 0 0 10  0
11     C    11 0 0 11  0
12     C    12 0 0 12  0
13     D    13 0 0  0 13
14     D    14 0 0  0 14
15     D    15 0 0  0 15
16     D    16 0 0  0 16

Or in base R:

cbind(df, 
      sapply(unique(df$Group), \(x) ifelse(df$Group == x, df$score, 0)))