r - 带有代表其他向量的独特组合的字母的新向量

Question

我有

dat <-data.frame(study=letters[c(1,1,1,4,4,4,4,10,10)],n1i=c(25,25,22,38,50,30,30,50,50)) 

我想要

     study n1i grp
1     a  25   A
2     a  25   A
3     a  22   B
4     d  38   A
5     d  50   B
6     d  30   C
7     d  30   C
8     j  50   A
9     j  50   A

但是这个...

dat$grp<-  
  as.vector(unlist(aggregate(dat$n1i,
   list(dat$study), function(x) LETTERS[1:length(x)])$x)) 

...给我

> dat
  study n1i grp
1     a  25   A
2     a  25   B
3     a  22   C
4     d  38   A
5     d  50   B
6     d  30   C
7     d  30   D
8     j  50   A
9     j  50   B

换句话说，我希望“grp”字母从 1 到最后一个唯一的 study*n1i 组合。

Answer 1

dat <-data.frame(study=letters[c(1,1,1,4,4,4,4,10,10)],n1i=c(25,25,22,38,50,30,30,50,50)) 

library(dplyr)

dat %>%
  group_by(study) %>%                    # for each study
  mutate(id = row_number()) %>%          # get the number of row as an id
  group_by(study, n1i) %>%               # for each study and n1i combination
  transmute(grp = LETTERS[min(id)]) %>%  # add the letters based on the minimum id value of that combination, while removing the id column
  ungroup()                              # forget the grouping

# # A tibble: 9 x 3
#   study   n1i grp  
#   <fct> <dbl> <chr>
# 1 a        25 A    
# 2 a        25 A    
# 3 a        22 C    
# 4 d        38 A    
# 5 d        50 B    
# 6 d        30 C    
# 7 d        30 C    
# 8 j        50 A    
# 9 j        50 A 

这种方法假设重复的行一个接一个。