How to select rows from data frame using grep() in R

Question

I am trying to select rows from a data frame based on the content of one of the columns. I am using grep() but when trying to match for the end of the content it only matches the last pattern that was submitted.

This is the code:

df1 <- data.frame(cName=c(
    'A Co', 'B Co',  'C Co', 'D Co', 
    'F Llc', 'G Llc', 'H Llc', 'I Llc',
    'P Inc', 'Q Inc', 'R Inc', 'S Inc'))    
tName <- grep( ("Inc$ | Llc$"),df1$cName, value = T)
tName
[1] "F Llc" "G Llc" "H Llc" "I Llc"

I am expecting it to return all the occurrences of 'Inc' and 'Llc'. However, only the last one in the regular expression is returned. I have tried various combinations with brackets, parenthesis and [:space:] without success. What is wrong? Thanks for any advice.

Ditch the white spaces they have meaning. In other words, just do grep("Inc$|Llc$",df1$cName, value = TRUE). Or in case space is important, do grep(" Inc$| Llc$",df1$cName, value = TRUE) — David Arenburg
– David Arenburg, Commented Mar 29, 2015 at 20:03

Wiktor Stribiżew · Accepted Answer · 2015-03-29 20:22:02Z

1

Here is the code that works as expected:

df1 <- data.frame(cName=c(
    'A Co', 'B Co',  'C Co', 'D Co', 
    'F Llc', 'G Llc', 'H Llc', 'I Llc',
    'P Inc', 'Q Inc', 'R Inc', 'S Inc'))    
tName <- grep( ("(Inc|Llc)$"),df1$cName, value = T)
tName

Output: [1] "F Llc" "G Llc" "H Llc" "I Llc" "P Inc" "Q Inc" "R Inc" "S Inc"

The original regex did not work as expected because it required a space after a string end anchor, which is just not possible. You can see the regex explanation at regex101.com.

answered Mar 29, 2015 at 20:22

Wiktor Stribiżew

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