I have a list of characters like this:
list <- c('a_b', 'a_c', 'a_d', 'a_e', 'a_b', 'b_a', 'b_c', 'b_c','c_b')
I want to have a list of unique characters with no more 'b_a', 'c_b'. I have tried unique() but it cannot remove 'b_a' and 'c_b'. I hope to receive some help about this. Many thanks!
You could use strsplit() to split the two characters apart, then sort them in alphabetical order and paste them back together. That will turn "b_a" into "a_b". Then you could get the unique values of the sorted strings.
l <- c('a_b', 'a_c', 'a_d', 'a_e', 'a_b', 'b_a', 'b_c', 'b_c','c_b')
ll <- strsplit(l, "_")
ll <- sapply(ll, \(x)paste(sort(x), collapse="_"))
unique(ll)
#> [1] "a_b" "a_c" "a_d" "a_e" "b_c"
Created on 2025-02-05 with reprex v2.1.1