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rregexdplyrmatchingmultiple-matches
agenis
agenis

Reputation: 8377

select columns based on multiple strings with dplyr contains()

I want to select multiple columns based on their names with a regex expression. I am trying to do it with the piping syntax of the dplyr package. I checked the other topics, but only found answers about a single string.

With base R:

library(dplyr)    
mtcars[grepl('m|ar', names(mtcars))]
###                      mpg am gear carb
### Mazda RX4           21.0  1    4    4
### Mazda RX4 Wag       21.0  1    4    4

However it doesn't work with the select/contains way:

mtcars %>% select(contains('m|ar'))
### data frame with 0 columns and 32 rows

What's wrong?

Upvotes: 60

Views: 60401

Answers (4)

redantman
redantman

Reputation: 31

here's an alternative

mtcars %>% 
    select(contains('m') | contains('ar')) %>% 
    head(2)

#             mpg am gear carb
# Mazda RX4      21  1    4    4
# Mazda RX4 Wag  21  1    4    4

Upvotes: 1

Nicki Norris
Nicki Norris

Reputation: 221

You can use contains from package dplyr, if you give a vector of text options, like this:

mtcars %>% 
       select(contains(c("m", "ar"))

Upvotes: 22

Muthoni Thiong'o
Muthoni Thiong'o

Reputation: 41

You could still use grepl() from base R.

df <- mtcars[ , grepl('m|ar', names(mtcars))]

...which returns a subset dataframe, df, containing columns with m or ar in the column names

Upvotes: 4

akrun
akrun

Reputation: 887118

You can use matches

 mtcars %>%
        select(matches('m|ar')) %>%
        head(2)
 #              mpg am gear carb
 #Mazda RX4      21  1    4    4
 #Mazda RX4 Wag  21  1    4    4

According to the ?select documentation

‘matches(x, ignore.case = TRUE)’: selects all variables whose name matches the regular expression ‘x’

Though contains work with a single string

mtcars %>% 
       select(contains('m'))

Upvotes: 116

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