Skip to contents

Select columns with a Stata varlist

Source: R/varlist.R
varlist.Rd

varlist() selects columns with a Stata-style varlist string such as "inc* age? x[1-12]", as in Stata's keep inc* age?. It is a simpler version of matches() in <tidy-select>.

Use varlist() within a selecting function, such as ds(), tab() or dplyr::across(). Alternatively, provide vars explicitly to return matching positions in a standalone call.

Usage

varlist(string, ignore_case = TRUE, vars = NULL)

Arguments

string

A single character string containing patterns, separated by spaces, like selecting a varlist in Stata's keep command.

ignore_case

If TRUE (the default), matching ignores case.

vars

A character vector of variable names. If not supplied, the variables are taken from the current selection context (as established by functions like select() or pivot_longer()).

Value

An integer vector of positions in the available column names.

Details

  • * matches zero or more characters.

  • ~ matches one or more characters.

  • ? matches one character.

  • [a-h] matches any character in the range from a to h.

  • [1-12] matches any number in the range from 1 to 12.

  • var1-var5 does not select a range of variables. Use var1:var5 outside varlist() instead.

Space-separated patterns are alternatives, each matched against complete column names. Numeric ranges expand within each pattern before matching. Each pattern can contain one bracketed range; separate patterns may each contain their own range.

See also

Other selection and preview functions: select_or_transmute(), special-print

Examples

varlist("x[1-2] y", vars = c("x1", "x2", "x3", "y"))
#> [1] 1 2 4

tb <- tibble::as_tibble(
  matrix(1:15, nrow = 1, dimnames = list(NULL, paste0("x", 1:15)))
)
tb
#> # A tibble: 1 x 15
#>      x1    x2    x3    x4    x5    x6    x7    x8    x9   x10   x11   x12   x13
#>   <int> <int> <int> <int> <int> <int> <int> <int> <int> <int> <int> <int> <int>
#> 1     1     2     3     4     5     6     7     8     9    10    11    12    13
#> # i 2 more variables: x14 <int>, x15 <int>

# List variable names by ds()
ds(tb)
#>  [1] "x1"  "x2"  "x3"  "x4"  "x5"  "x6"  "x7"  "x8"  "x9"  "x10" "x11" "x12"
#> [13] "x13" "x14" "x15"

tb |>
  ds(varlist("x1*"))
#> [1] "x1"  "x10" "x11" "x12" "x13" "x14" "x15"

tb |>
  ds(varlist("x1~"))
#> [1] "x10" "x11" "x12" "x13" "x14" "x15"

tb |>
  ds(varlist("*5"))
#> [1] "x5"  "x15"

tb |>
  ds(varlist("?5"))
#> [1] "x5"

tb |>
  ds(varlist("x[9-15]"))
#> [1] "x9"  "x10" "x11" "x12" "x13" "x14" "x15"

# A literal hyphen pattern selects no columns here; it is not a range.
tb |>
  ds(varlist("x1-x5"))
#> character(0)