dplyr: select helpers + tidyeval
For a recent project, a dataset’s columns were indicator variables for options selected from drop-down menus. The column names consisted of the menu name suffix-ed with the option number (ex. a___1 is the first option from menu a). The data dictionary only included menu names. I wanted to leverage dplyr’s starts_with() to select columns for multiple menus without hard-coding each starts_with().
Programatically select columns with dplyr’s select helpers
library(tidyverse)
df <- data.frame(
'a___1' = c(1, 0), 'a___2' = c(0, 1),
'b___1' = c(1, 0), 'b___2' = c(0, 1),
'c___1' = c(1, 0), 'c___2' = c(0, 1)
)
df
#> a___1 a___2 b___1 b___2 c___1 c___2
#> 1 1 0 1 0 1 0
#> 2 0 1 0 1 0 1
vars <- c('a', 'b')
quo_vars <- map(vars, ~quo(starts_with(.)))
df %>% select(!!!quo_vars)
#> a___1 a___2 b___1 b___2
#> 1 1 0 1 0
#> 2 0 1 0 1
Created on 2018-10-21 by the reprex package (v0.2.1)
Session info
devtools::session_info()
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#> date 2018-10-21
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