Question

I’d like to ask a follow-up question to this issue, please, because an additional problem arose: I discovered subjects (Cultural Studies, e.g.) which belong to more than one category (Arts & Humanities and Social Sciences), i.e. there is overlap which has to be considered.

I have long lists of categories such as this machine readable example:

AB <- c("Science","Arts & Humanities","Arts & Humanities; Social Sciences","Science","Arts & Humanities; Arts & Humanities; Social Sciences","Science","Science; Social Sciences","Social Sciences; Science")  

So it looks like this:

> AB  
[1] "Science"                                               "Arts & Humanities"  
[3] "Arts & Humanities; Social Sciences"                    "Science"  
[5] "Arts & Humanities; Arts & Humanities; Social Sciences" "Science"  
[7] "Science; Social Sciences"                              "Social Sciences; Science"  

I would like to edit these terms and eliminate duplicates in order to get this result:

[1] "Science"                                    "Arts & Humanities"  
[3] "Arts & Humanities; Social Sciences"         "Science"  
[5] "Arts & Humanities; Social Sciences"         "Science"  
[7] "Science; Social Sciences"                   "Science; Social Sciences"  

So I’m looking for another loop to eliminate the duplicate in #5. I tried using strsplit() and unique() but this didn’t work:

> unique(strsplit(AB, "; *"))  
[[1]]  
[1] "Science"  

[[2]]  
[1] "Arts & Humanities"  

[[3]]  
[1] "Arts & Humanities" "Social Sciences"  

[[4]]  
[1] "Arts & Humanities" "Arts & Humanities" "Social Sciences"  

[[5]]  
[1] "Social Sciences" "Science"  

So I would like to ask you again, please: How can I achieve the correct output mentioned above?
Thank you very much in advance for your consideration!

Answer 1

I think it has to do with a trailing or leading white space. If you apply this to AB it will take care of this for you:

fun <- function(text.var){
    x <- unlist(strsplit(text.var, ";"))
    Trim <- function(x) gsub("^\\s+|\\s+$", "", x)
    paste(sort(unique(Trim(x))), collapse="; ")
}

sapply(AB, fun, USE.NAMES = FALSE)

Yielding:

> sapply(AB, fun, USE.NAMES = FALSE)
[1] "Science"                            "Arts & Humanities"                 
[3] "Arts & Humanities; Social Sciences" "Science"                           
[5] "Arts & Humanities; Social Sciences" "Science"                           
[7] "Science; Social Sciences"           "Science; Social Sciences"