How to delete words before and after a specific word inside a string, using R?

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I have the following df:

structure(list(id = c(9L, 10L, 11L, 96L, 97L, 101L, 103L, 248L, 
499L, 1044L), leg_activity = c("home, adpt, shop, car_passenger, home, adpt, work, adpt, home pt,, work pt,, outside, outside, outside pt,, outside pt,, pt, home", 
"home pt,, pt, outside, outside, outside, outside pt,, pt, home, car, leisure, car, other, car, leisure, car, leisure, car, other, car, leisure, car, other, car, leisure, car, home, adpt, leisure, adpt, home", 
"home pt,, work, adpt, home", "home, car, work, car, home pt,, work, adpt, home", 
"home, adpt, work, car_passenger, leisure, car_passenger, work, adpt, home, car_passenger, outside, outside, outside, car_passenger, outside, outside, outside, car_passenger, home", 
"home, bike, outside, outside, outside, car_passenger, outside, outside, outside, car_passenger, outside, outside, outside, bike, home, adpt, leisure, adpt, home, bike, leisure, bike, home", 
"home, adpt, work, adpt, home, walk, other, pt, home", "home, adpt, work, walk, home, adpt, work, walk, home", 
"home, adpt, leisure, adpt, home, bike, outside, outside, outside, bike, home", 
"home, pt, work, adpt, home, adpt, work, adpt, home")), row.names = c(NA, 
10L), class = "data.frame")

As you can see, the leg_activity column contains strings. What I want is to delete all the words, which are in a connection with the word outside.

To be a bit more specific, lets take hypothetical row as an example:

"home, bike, outside, outside, outside, car_passenger, outside, outside,  bike, home, adpt, bike, leisure, bike, home"

The goal is to delete the word that comes before outside as well as the one after outside and eventually, outsideought to be deleted too. The desired output:

"home, home, adpt, bike, leisure, bike, home"

So far I'm only able to delete the specific word

agents$leg_activity <- gsub(', home', '', agents$leg_activity)

Thank you very much for your help!

gsub r
1 Answers

We can split the string on a comma, get the position of where "outside" is present using grep and remove the values before and after it. 

agents$new_col <- sapply(strsplit(agents$leg_activity, ',{1,}\\s'), function(x) {
              inds <-  grep('outside', x)
              if(length(inds)) toString(x[-unique(c(inds - 1, inds, inds + 1))])
              else toString(x)
})
agents$new_col

# [1] "home, adpt, shop, car_passenger, home, adpt, work, adpt, home pt, home"                                                                                       
# [2] "home pt, home, car, leisure, car, other, car, leisure, car, leisure, car, other, car, leisure, car, other, car, leisure, car, home, adpt, leisure, adpt, home"
# [3] "home pt, work, adpt, home"                                                                                                                                    
# [4] "home, car, work, car, home pt, work, adpt, home"                                                                                                              
# [5] "home, adpt, work, car_passenger, leisure, car_passenger, work, adpt, home, home"                                                                              
# [6] "home, home, adpt, leisure, adpt, home, bike, leisure, bike, home"                                                                                             
# [7] "home, adpt, work, adpt, home, walk, other, pt, home"                                                                                                          
# [8] "home, adpt, work, walk, home, adpt, work, walk, home"                                                                                                         
# [9] "home, adpt, leisure, adpt, home, home"                                                                                                                        
#[10] "home, pt, work, adpt, home, adpt, work, adpt, home"
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