Separate string after last underscore

Question

This is indeed a duplicate for this question r-split-string-using-tidyrseparate, but I cannot use the MWE for my purpose, because I do not know how to adjust the regular Ex

Answer 1

Here's an alternative data.table solution using tstrsplit/melt/dcast I would personally stick with data.table in this case because spread doesn't have a fun argument, hence, if you have dupes when spreading again, you will get an error.

library(magrittr) # people like pipes these days
dt %>%
  # convert ot long format like you did
  melt(., id = "Name") %>% 
  # split by the last underscore
  .[, c("variable", "grp") := tstrsplit(variable, "_(?!.*_)", perl = TRUE)] %>% 
  # convert back to wide format
  dcast(., Name + grp ~ variable) 

#    Name grp Var_1 Var_2
# 1:    A BdS    NA    NA
# 2:    A EVU     2    NA
# 3:    B BdS     3     3
# 4:    B EVU    NA    NA
# 5:    C BdS     4     4
# 6:    C EVU    NA    NA