I need to concatenate strings by group in the dplyr, but the resulting column should account only for the previous columns, not the leading ones

I want my data to look like this:

Is it achievable using dplyr only?

CodePudding user response：

You can use Reduce(..., accumulate = TRUE) from base:

library(dplyr)

df %>%
  group_by(ID) %>%
  mutate(messages_used = Reduce(\(x, y) paste(x, y, sep = ", "), message, accumulate = TRUE)) %>%
  ungroup()

# # A tibble: 5 x 3
#      ID message messages_used
#   <int>   <int> <chr>
# 1     1      53 53
# 2     1      54 53, 54
# 3     1      55 53, 54, 55
# 4     2      53 53
# 5     2      58 53, 58

CodePudding user response：

We can use dplyr::group_by() and purrr::accumulate():

dat <- data.frame(ID = c(1,1,1,2,2), message = c(53,54,55,53,58))

library(dplyr)
library(purrr)

dat %>% 
  group_by(ID) %>% 
  mutate(message_used = accumulate(message, ~ paste(.x, .y, sep =",")))
#> # A tibble: 5 x 3
#> # Groups:   ID [2]
#>      ID message message_used
#>   <dbl>   <dbl> <chr>       
#> 1     1      53 53          
#> 2     1      54 53,54       
#> 3     1      55 53,54,55    
#> 4     2      53 53          
#> 5     2      58 53,58

^{Created on 2022-05-11 by the reprex package (v2.0.1)}