Replace multiple words with a word single word

user_5408255 0
Viewed 313

I want to replace multiple letters/words with a single letter/word, multiple times in a dataframe. As an example,

Some data:

df = data.frame(
      a = 1:8, 
      b = c("colour1 o", "colour2 O", "colour3 out",  "colour4 Out", 
            "soundi i", "soundr I", "sounde in", "soundw In"))

df
  a           b
1 1   colour1 o
2 2   colour2 O
3 3   colour3 out
4 4   colour4 Out
5 5    soundi i
6 6    soundr I
7 7    sounde in
8 8    soundw In

Here is what I want to replace with:

df_repl <- list(
  O = c("o", "out", "Out"),
  In = c("i", "in", "I"))

So in df$b o, out and Out should become O and i, in and I become In, but only if they are separated from any other words by a space, so o in colour is not capitalised.

This gets me half way there, but I think I need another nested for-loop to move through df_repl... 

for (word in df_repl[[1]]){
  patt <- paste0('\\b', word, '\\b')
  repl <- paste(names(df_repl[1]))
  df$b <- gsub(patt, repl, df$b)
}

df
  a         b
1 1 colour1 O
2 2 colour2 O
3 3 colour3 O
4 4 colour4 O
5 5  soundi i
6 6  soundr I
7 7  sounde in
8 8  soundw In

Above o, out and Out become O but i, in and I are not altered, here is the desired output:

  a         b
1 1 colour1 O
2 2 colour2 O
3 3 colour3 O
4 4 colour4 O
5 5  soundi In
6 6  soundr In
7 7  sounde In
8 8  soundw In

In the real data there are many more than two replacement words/letters so I can't just rerun the for-loop again. I'm not tied to a for-loop solution, but preferably using base R, any suggestions much appreciated.

EDIT

Trying to clarify my question:

Whenever one of o, out or Out occur in df$b I want to replace it with O

Whenever one of i, in or I occur in df$b I want to replace it with In

I can achieve the desired output like this:

for (word in df_repl[[1]]){
  patt <- paste0('\\b', word, '\\b')
  repl <- paste(names(df_repl[1]))
  df$b <- gsub(patt, repl, df$b)
}

for (word in df_repl[[2]]){
  patt <- paste0('\\b', word, '\\b')
  repl <- paste(names(df_repl[2]))
  df$b <- gsub(patt, repl, df$b)
}

But in my real dataset df_repl is length 50 rather two so I don't want to copy/paste/edit/rerun the for-loop 50 times

gsub r replace string
3 Answers

You may try using three separate calls to sub:

df$b <- sub("\\bo\\b", "i", df$b)
df$b <- sub("\\bout\\b", "in", df$b)
df$b <- sub("\\bOut\\b", "I", df$b)

df

  a          b
1 1  colour1 i
2 2  colour2 O
3 3 colour3 in
4 4  colour4 I
5 5   soundi i
6 6   soundr I
7 7  sounde in
8 8  soundw In

To automate this, you could try using sapply with an index:

terms_in <- c("o", "out", "Out")
pat <- paste0("\\b", terms_in, "\\b")
replace <- c("i", "in", "I")
sapply(seq_along(pat), function(x) {
    df$b <<- sub(pat[x], replace[x], df$b)
})
user_18632290

This is another solution: 

library(stringr)
in1 <- str_split(df$b, " ", simplify = TRUE)[,1]
in2 <- str_split(df$b, " ", simplify = TRUE)[,2]

in2[in2 %in% c("o", "out", "Out")] <- "O"
in2[in2 %in% c("i", "in", "I")] <- "In"
df$b <- paste(in1, in2, sep=" ") 
df

If you have a long list of words in your data, you could also move c(word list) outside: 

in1<- str_split(df$b, " ", simplify = TRUE)[,1]
in2<- str_split(df$b, " ", simplify = TRUE)[,2]
o <- c("o", "Out", "Out")
i <- c("i", "in", "I") 
in2[in2 %in% o] <- "O"
in2[in2 %in% i] <- "In"
df$b <- paste(in1, in2, sep=" ") 
df

> df
  a         b
1 1 colour1 O
2 2 colour2 O
3 3 colour3 O
4 4 colour4 O
5 5 soundi In
6 6 soundr In
7 7 sounde In
8 8 soundw In
user_117419430

You can skip the loop over the words in df_repl when you paste them with | (or) between the words like:

for(i in names(df_repl)) {
    df$b <- sub(paste(paste0("\\b",df_repl[[i]],"\\b"), collapse = "|")
                , i, df$b)
}
df
#  a         b
#1 1 colour1 O
#2 2 colour2 O
#3 3 colour3 O
#4 4 colour4 O
#5 5 soundi In
#6 6 soundr In
#7 7 sounde In
#8 8 soundw In
user_104885040
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