Select columns using starts_with()

Question

With select(starts_with("A") I can select all the columns in a dataframe/tibble starting with "A".

But how can I select all the columns in a dataframe/tibble starting with one of the letters in a vector?

Example:

columns_to_select <- c("A", "B", "C")
df %>% select(starts_with(columns_to_select))

I would like to select A1, A2, A3... and B1, B2, B3, ... and C1, C2, Cxy...

Answer 1

This currently seems to be working the way you're describing:

library(tidyverse)

df <- tibble(A1 = 1:10, B1 = 1:10, C3 = 21:30, D2 = 11:20)

columns_to_select <- c("A", "B", "C")

df |> 
  select(starts_with(columns_to_select))
#> # A tibble: 10 × 3
#>       A1    B1    C3
#>    <int> <int> <int>
#>  1     1     1    21
#>  2     2     2    22
#>  3     3     3    23
#>  4     4     4    24
#>  5     5     5    25
#>  6     6     6    26
#>  7     7     7    27
#>  8     8     8    28
#>  9     9     9    29
#> 10    10    10    30

Do you mean to select only by one of the letters at a time? (you can use columns_to_select[1] for this) Apologies if I've misunderstood the question - can delete this response if not relevant.