R - removing substring in column of strings based on pattern and condition

user_16281641 0
Viewed 64

I have a column of strings in a data frame where I would like to replace the values to include only the substring before the first " (", i.e., before the first space/open bracket pair. Not all of the strings contain brackets, and I want those to be left as they are.

Example data:

col1 <- c(1, 2, 3, 4)
col2 <- c("a b (ABC DE)", "bcd", "cd ef (CE)", "bcd")
df <- data.frame(col1, col2)
df

Output:

  col1       col2
1    1 a b (ABC DE)
2    2        bcd
3    3  cd ef (CE)
4    4        bcd

The output I'm looking for would be something like this:

col1 <- c(1, 2, 3, 4)
col2 <- c("a b", "bcd", "cd ef", "bcd")
df <- data.frame(col1, col2)
df

Output:

  col1 col2
1    1  a b
2    2  bcd
3    3 cd ef
4    4  bcd

The actual data frame is 40000+ rows with the strings taking many possible values, so it can't be done manually like in the example. I'm not confident at all working with regex/patterns, but accept this may be the most straightforward way to do this.

dataframe substring r string
4 Answers

Here's a dplyr method

library(dplyr)
library(stringr)

df %>% 
  mutate(col2 = str_replace_all(col2, "\\(.+?\\)", ""))

Which returns the df:

  col1   col2
1    1   a b 
2    2    bcd
3    3 cd ef 
4    4    bcd
user_129679380

A possible solution, based on stringr:

library(tidyverse)

df %>% 
  mutate(col2 = str_remove_all(col2, "\\s*\\(.*\\)\\s*"))

#>   col1  col2
#> 1    1   a b
#> 2    2   bcd
#> 3    3 cd ef
#> 4    4   bcd
user_115644870

Using R base gsub

> df$col2 <- gsub("\\s*\\(.*\\)", "", df$col2)
> df
  col1  col2
1    1   a b
2    2   bcd
3    3 cd ef
4    4   bcd
user_13157670

I'd rather use a regex than substrings.

transform(df, col2=gsub('\\s+\\(.*', '', x))
#   col1 col2
# 1    1   ab
# 2    2  bcd
# 3    3 cedf
# 4    4  bcd
user_65740380
Related