dplyr::starts_with and ends_with not subsetting based on arguments

Question

I want to select a number of variables based on thier names to transform them. The variable names all start with inq and end with 7, 8, 10, 13:15 . This is not working for me... Apologies if this is obvious, but I cannot get it to work. Am I using the wrong functions, putting my functions and arguments together wrong, or something else?

A reproducible example:

structure(list(inq1_1 = c(NA, 7, 5, 1, 1, 6, 5, 2, NA, NA), inq1_2 = c(NA, 
7, 5, 1, 1, 6, 5, 5, NA, NA), inq1_3 = c(NA, 6, 4, 2, 1, 5, 2, 
1, NA, NA), inq1_4 = c(NA, 6, 6, 1, 1, 6, 5, 1, NA, NA), inq1_5 = c(NA, 
7, 3, 1, 1, 6, 2, 1, NA, NA), inq1_6 = c(NA, 7, 4, 4, 2, 7, 2, 
4, NA, NA), inq1_7 = c(NA, 2, 4, 6, 7, 3, 1, 7, NA, NA), inq1_8 = c(NA, 
1, NA, 2, 7, 2, 1, 4, NA, NA), inq1_9 = c(NA, 4, 6, 3, 1, 3, 
7, 1, NA, NA), inq1_10 = c(NA, 3, 5, 7, 4, 4, 2, 7, NA, NA), 
    inq1_11 = c(NA, 5, 4, 7, 1, 6, 7, 6, NA, NA), inq1_12 = c(NA, 
    7, 5, 7, 4, 6, 7, 2, NA, NA), inq1_13 = c(NA, 3, 4, 6, 4, 
    3, 4, 4, NA, NA), inq1_14 = c(NA, 3, 2, 4, 4, 2, 1, 4, NA, 
    NA), inq1_15 = c(NA, 2, 2, 3, 5, 2, 4, 4, NA, NA), inqfinal_1 = c(5, 
    NA, 3, NA, NA, NA, NA, NA, NA, NA), inqfinal_2 = c(5, NA, 
    3, NA, NA, NA, NA, NA, NA, NA), inqfinal_3 = c(6, NA, 3, 
    NA, NA, NA, NA, NA, NA, NA), inqfinal_4 = c(5, NA, 3, NA, 
    NA, NA, NA, NA, NA, NA), inqfinal_5 = c(5, NA, 3, NA, NA, 
    NA, NA, NA, NA, NA), inqfinal_6 = c(6, NA, 3, NA, NA, NA, 
    NA, NA, NA, NA), inqfinal_7 = c(4, NA, 3, NA, NA, NA, NA, 
    NA, NA, NA), inqfinal_8 = c(2, NA, 3, NA, NA, NA, NA, NA, 
    NA, NA), inqfinal_9 = c(5, NA, 3, NA, NA, NA, NA, NA, NA, 
    NA), inqfinal_10 = c(4, NA, 3, NA, NA, NA, NA, NA, NA, NA
    ), inqfinal_11 = c(6, NA, 4, NA, NA, NA, NA, NA, NA, NA), 
    inqfinal_12 = c(6, NA, 4, NA, NA, NA, NA, NA, NA, NA), inqfinal_13 = c(4, 
    NA, 3, NA, NA, NA, NA, NA, NA, NA), inqfinal_14 = c(2, NA, 
    2, NA, NA, NA, NA, NA, NA, NA), inqfinal_15 = c(2, NA, 2, 
    NA, NA, NA, NA, NA, NA, NA)), row.names = c(NA, -10L), class = c("tbl_df", 
"tbl", "data.frame"))

I am trying to become tidy and utilising dplyr as per the code below:

# select specific columns
sf_df %>% select(starts_with("inq"),
                 ends_with(7, 8, 10, 13:15)) %>% view(title = "test")

Alas, I get the following error:

Error in ends_with(7, 8, 10, 13:15) : unused argument (13:15)
14. .f(.x[[i]], ...)
13. map(.x[sel], .f, ...)
12. map_if(ind_list, is_helper, eval_tidy)
11. vars_select_eval(.vars, quos)
10. tidyselect::vars_select(names(.data), !!!quos(...))
9. select.data.frame(., starts_with("inq"), ends_with(7, 8, 10, 13:15))
8. select(., starts_with("inq"), ends_with(7, 8, 10, 13:15))
7. function_list[[i]](value)
6. freduce(value, `_function_list`)
5. `_fseq`(`_lhs`)
4. eval(quote(`_fseq`(`_lhs`)), env, env)
3. eval(quote(`_fseq`(`_lhs`)), env, env)
2. withVisible(eval(quote(`_fseq`(`_lhs`)), env, env))
1. sf_df %>% select(starts_with("inq"), ends_with(7, 8, 10, 13:15)) %>% view(title = "test")

Any help would be greatly appreciated! Thank you in advance.

Cheers, Atanas.

Answer 1

A better option would be matches to match a regex pattern in the column name. Here, it matches the pattern 'ing' at the beginning ( ^ ) of the column name and numbers at the end ( $ ) of the column name

sf_df %>% 
    select(matches('^inq.*(7|8|10|13|14|15)$'))
# A tibble: 10 x 12
#   inq1_7 inq1_8 inq1_10 inq1_13 inq1_14 inq1_15 inqfinal_7 inqfinal_8 inqfinal_10 inqfinal_13 inqfinal_14 inqfinal_15
#    <dbl>  <dbl>   <dbl>   <dbl>   <dbl>   <dbl>      <dbl>      <dbl>       <dbl>       <dbl>       <dbl>       <dbl>
# 1     NA     NA      NA      NA      NA      NA          4          2           4           4           2           2
# 2      2      1       3       3       3       2         NA         NA          NA          NA          NA          NA
# 3      4     NA       5       4       2       2          3          3           3           3           2           2
# 4      6      2       7       6       4       3         NA         NA          NA          NA          NA          NA
# 5      7      7       4       4       4       5         NA         NA          NA          NA          NA          NA
# 6      3      2       4       3       2       2         NA         NA          NA          NA          NA          NA
# 7      1      1       2       4       1       4         NA         NA          NA          NA          NA          NA
# 8      7      4       7       4       4       4         NA         NA          NA          NA          NA          NA
# 9     NA     NA      NA      NA      NA      NA         NA         NA          NA          NA          NA          NA
#10     NA     NA      NA      NA      NA      NA         NA         NA          NA          NA          NA          NA

---

Note that by using both starts_with and ends_with , the desired result may not be the expected one. The OP's dataset has 30 columns where all the column names start with 'inq'. So, with starts_with , it returns all columns, and adding ends_with , it is checking an OR match, eg

sf_df %>% 
     select(starts_with("inq"), ends_with("5")) %>%
     ncol
#[1] 30 # returns 30 columns

It is not removing the columns that have no match for 5 at the string

It is not a behavior of the order of arguments as

sf_df %>%
  select(ends_with("5"), starts_with("inq")) %>%
  ncol
#[1] 30

Now, if we use only ends_with

sf_df %>% 
  select(ends_with("5")) %>% 
  ncol
#[1] 4

Based on the example, all columns starts with 'inq', so, ends_with alone would be sufficient for a single string match as the documentation for ?ends_with specifies

match - A string.

and not multiple strings

where the Usage is

starts_with(match, ignore.case = TRUE, vars = peek_vars())