For loop over list of items to use in R's gsub

Question

In R, I want to loop over items to replace in a column.

the input into the function is a list of items and I want to return the list after removing any and all items within itemsToBeRemoved list.

removePunctuation <- function(punctuationObject){
    itemsToBeRemoved <- list(".", ",", ";", ":", "'", "!", "#", "-", "--")
    objectApplyTo <- punctuationObject
    for (itemToReplace in itemsToBeRemoved){
        resultObject <- gsub("itemToReplace", "", objectApplyTo, fixed=TRUE)
        return(resultObject)   
    }
}

I expect all instances of ".", ",", ";", ":", "'", "!", "#", "-", "--" to be removed from a list of character elements.

Check out package `stringr`, vectorized function `str_remove_all`. — Rui Barradas, Jul 09 '19 at 19:15
Also, your code has 2 errors: 1) `gsub("itemToReplace", etc)` with quotes. They are not needed, like this you are removing the *string* `"itemToReplace"` not the *variable* `itemToReplace`. 2) It returns after the first time through the loop. — Rui Barradas, Jul 09 '19 at 19:17
Thanks, that's my constant manipulating it to work. I removed the quotes and placed return at end of loop but still nothing was removed. — Chris, Jul 09 '19 at 19:24
'''removePunctuation <- function(punctuationObject){ itemsToBeRemoved <- list(".", ",", ";", ":", "'", "!", "#", "-", "--") objectApplyTo <- punctuationObject for (itemToReplace in itemsToBeRemoved){ resultObject <- gsub(itemToReplace, "", objectApplyTo, fixed=TRUE) } return(resultObject) }''' — Chris, Jul 09 '19 at 19:24
just used the [[:punct:]] method. That worked but I need flexibility to remove other items that might be specific strings — Chris, Jul 09 '19 at 19:26
@Chris you can add them with `|`. Try `gsub("[[:punct:]]|fox", "", "The.Quick,brown;fox:jumps'over!the#lazy-dogs--")`. — jay.sf, Jul 09 '19 at 19:28
That does work and I added other items to get more familiar against my own data set. I'm still a bit confused how I could remove just a period and a backslash. Would I just use "\\." and "\\\" to specifically remove a period or backslash? — Chris, Jul 09 '19 at 19:52
@Chris Yes also separated by `|`, backslashes are nasty, though, `gsub("\\\\|\\.", "", "Do \\re mi.")`, see [this answer](https://stackoverflow.com/a/25427271/6574038). — jay.sf, Jul 10 '19 at 09:34

score 2 · Accepted Answer · answered Jul 09 '19 at 19:30

A base R solution could be

removePunctuation <- function(punctuationObject){
  itemsToBeRemoved <- c(".", ",", ";", ":", "'", "!", "#", "-", "--")
  resultObject <- punctuationObject
  for (itemToReplace in itemsToBeRemoved){
    resultObject <- gsub(itemToReplace, "", resultObject, fixed = TRUE)
  }
  resultObject
}

x <- c("This, that; end.", "Second: single quote' etc !")

removePunctuation(x)
#[1] "This that end"            "Second single quote etc "

score 1 · Answer 2 · answered Jul 09 '19 at 19:37

You have several problems, one of them is that if you want to make it work in a list, you are overriding constantly the values of it. Also the pattern "." it's problematic for you. Because it takes it as the "." wildcard, not just a plain dot. Check this:

removePunctuation <- function(punctuationObject){
  itemsToBeRemoved <- list("\\.", ",", ";", ":", "'", "!", "#", "-", "--")
  for (item in itemsToBeRemoved){
    punctuationObject <- gsub(item, "", punctuationObject)
    print(punctuationObject)

  }
  return(punctuationObject)  
}

punctuationObject <- list("a,", "b", "c#")


removePunctuation(punctuationObject)

For loop over list of items to use in R's gsub

2 Answers2

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