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Problem with the str_replace function

4 messages · Bert Gunter, Hervé Pagès, phii m@iii@g oii phiiipsmith@c@

Original
phii m@iii@g oii phiiipsmith@c@
# 
I have a problem with the str_replace() function in the stringr package. 
Please refer to my reprex below.

I start with a vector of strings, called x. Some of the strings contain 
apostrophes and brackets. I make a simple replacement as with x1, and 
there is no problem. I make another simple replacement, x2, where the 
pattern string has an apostrophe. Again no problem. Then I make a third 
replacement, x3, where the pattern has opening and closing brackets and 
the function still works fine. Finally I make a replacement where the 
pattern has both an apostrophe and opening and closing brackets and the 
replacement does not work. I tried to solve this by putting backslashes 
before the apostrophe and/or the brackets, but that accomplished 
nothing. I am stumped.

# Reprex for str_replace problem

library(stringr)

x <- c(
   "Clothing and footwear",
   "Women's clothing",
   "Women's footwear (excluding athletic)",
   "Clothing accessories (belts and so on)",
   "Clothing and footwear",
   "Women's clothing",
   "Women's footwear (excluding athletic)",
   "Clothing accessories (belts and so on)"
)
x
x1 <- str_replace(x,
   "Clothing and footwear",
   "Clothing and shoes"
)
x1
x2 <- str_replace(x,
   "Women's clothing",
   "Women's clothing goods"
)
x2
x3 <- str_replace(x,
   "Clothing accessories (belts and so on)",
   "Clothing accessories")
x3
x4 <- str_replace(x,
   "Women's footwear (excluding athletic)",
   "Women's footwear")
x4
Bert Gunter
# 
I prefer using regular expressions directly, so this may not satisfy you:
[1] "Women's footwear"

There are, of course other ways to do this with regex's or even substring()

Bert Gunter

"The trouble with having an open mind is that people keep coming along and
sticking things into it."
-- Opus (aka Berkeley Breathed in his "Bloom County" comic strip )
On Tue, Mar 16, 2021 at 5:36 PM <phil at philipsmith.ca> wrote:

            

      
      
      
    

        

      
      
    

        

  
  


  


      

    

    

      
      

        


  

        

      Hervé Pagès
    

    

      
      #
    

  


  

      
Hi,

stringr::str_replace() treats the 2nd argument ('pattern') as a regular 
expression and some characters have a special meaning when they are used 
in a regular expression. For example the dot plays the role of a 
wildcard (i.e. it means "any character"):

   > str_replace("aaXcc", "a.c", "ZZ")
   [1] "aZZc"

If you want to treat a special character literally, you need to escape 
it with a double backslahe '\\':

   > str_replace(c("aaXcc", "aa.cc"), "a.c", "ZZ")
   [1] "aZZc" "aZZc"

   > str_replace(c("aaXcc", "aa.cc"), "a\\.c", "ZZ")
   [1] "aaXcc" "aZZc"

Turns out that parenthesis are also special characters so you also need 
to escape them:

   > str_replace("aa(X)cc", "a(X)c", "ZZ")
   [1] "aa(X)cc"

   > str_replace("aa(X)cc", "a\\(X\\)c", "ZZ")
   [1] "aZZc"

There are plenty of example in the man page for str_replace() (see 
'?str_replace') including examples showing the use of parenthesis in the 
pattern.

Hope this helps,

H.

        
On 3/16/21 5:34 PM, phil at philipsmith.ca wrote:

            

      
      
      
    

        

      
      
    

        

  
    

      
      
    

  


  


      

    

    

      
      

        


  

        

      phii m@iii@g oii phiiipsmith@c@
    

    

      
      #
    

  


  

      
Your help is much appreciated. I now understand what my problem was and 
can move forward.

Philip

        
On 2021-03-17 01:19, Herv? Pag?s wrote: