dplyr::starts_with and ends_with not subsetting based on arguments - r

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, e.g.
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())