How do keep only unique words within each string in a vector

I have data that looks like this:

vector = c("hello I like to code hello","Coding is fun", "fun fun fun")

I want to remove duplicate words (space delimited) i.e. the output should look like

vector_cleaned

[1] "hello I like to code"
[2] "coding is fun"
[3] "fun"

Split it up (strsplit on spaces), use unique (in lapply), and paste it back together:

vapply(lapply(strsplit(vector, " "), unique), paste, character(1L), collapse = " ")
# [1] "hello i like to code" "coding is fun"        "fun"  

## OR
vapply(strsplit(vector, " "), function(x) paste(unique(x), collapse = " "), character(1L))

Update based on comments

You can always write a custom function to use with your vapply function. For instance, here's a function that takes a split string, drops strings that are shorter than a certain number of characters, and has the "unique" setting as a user choice.

myFun <- function(x, minLen = 3, onlyUnique = TRUE) {
  a <- if (isTRUE(onlyUnique)) unique(x) else x
  paste(a[nchar(a) > minLen], collapse = " ")
}

Compare the output of the following to see how it would work.

vapply(strsplit(vector, " "), myFun, character(1L))
vapply(strsplit(vector, " "), myFun, character(1L), onlyUnique = FALSE)
vapply(strsplit(vector, " "), myFun, character(1L), minLen = 0)

I spent a while looking for a data frame, tidyverse-friendly version of this, so figured I'd paste my verbose solution:

library(tidyverse)

df <- data.frame(vector = c("hello I like to code hello",
                            "Coding is fun", 
                            "fun fun fun"))

df %>% 
  mutate(split = str_split(vector, " ")) %>% # split
  mutate(split = map(.$split, ~ unique(.x))) %>% # drop duplicates
  mutate(split = map_chr(.$split, ~paste(.x, collapse = " "))) # recombine

Result:

#>                       vector                split
#> 1 hello I like to code hello hello I like to code
#> 2              Coding is fun        Coding is fun
#> 3                fun fun fun                  fun

^{Created on 2021-01-03 by the reprex package (v0.3.0)}