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rselectquoteexpr

select column names containing string programmatically

Given a data frame like:

df <- data.frame(z_a = 1:2,
                 z_b = 1:2,
                 y_a = 3:4,
                 y_b = 3:4)

I can select columns names that contain a character with:

library(dplyr)
df %>% select(contains("a"), contains("b"))

  z_a y_a z_b y_b
1   1   3   1   3
2   2   4   2   4

NOTE that the column order has changed. Columns containing a come first before columns containing b

I'd like to select column names that contain characters in a vector and that reorders the columns.

searchfor <- letters[1:2]

Using searchfor, I'd like to make the following expression and use it in a select statement:

E <- quote(contains(searchfor[1]), contains(searchfor[2]))
df %>% select_(E)
Solution

  • We can do 

    df %>% 
   select_at(vars(matches(paste(searchfor, collapse="|")))) %>%
   select(order(sub(".*_", "", names(.))))