Shortest way to remove duplicate words from string-CodePudding

I have this string:

x <- c("A B B C")

[1] "A B B C"

I am looking for the shortest way to get this:

[1] "A B C"

I have tried this: Removing duplicate words in a string in R

paste(unique(x), collapse = ' ')

[1] "A B B C"
# does not work

Background: In a dataframe column I want to count only the unique word counts.

CodePudding user response：

A regex based approach could be shorter - match the non-white space (\\S ) followed by a white space character (\\s), capture it, followed by one or more occurrence of the backreference, and in the replacement, specify the backreference to return only a single copy of the match

gsub("(\\S \\s)\\1 ", "\\1", x)
[1] "A B C"

Or may need to split the string with strsplit, unlist, get the unique and then paste

paste(unique(unlist(strsplit(x, " "))), collapse = " ")
# [1] "A B C"

CodePudding user response：

Another possible solution, based on stringr::str_split:

library(tidyverse)

str_split(x, " ") %>% unlist %>% unique

#> [1] "A" "B" "C"

CodePudding user response：

You can use ,

gsub("\\b(\\w )(?:\\W \\1\\b) ", "\\1", x)

CodePudding user response：

Just in case the duplicates are not following each other, also using gsub.

gsub("(\\S )\\s*(?=.*\\b\\1\\b)", "", x, perl=TRUE)
#[1] "A B C"

gsub("(\\S )\\s*(?=.*\\b\\1\\b)", "", "A B B A", perl=TRUE)
#[1] "B A"