poorman (version 0.2.6)

select_helpers: Select Helpers

Description

These functions allow you to select variables based on their names.

• starts_with(): Starts with a prefix.

• ends_with(): Ends with a prefix.

• contains(): Contains a literal string.

• matches(): Matches a regular expression.

• all_of(): Matches variable names in a character vector. All names must be present, otherwise an error is thrown.

• any_of(): The same as all_of() except it doesn't throw an error.

• everything(): Matches all variables.

• last_col(): Select the last variable, possibly with an offset.

Usage

starts_with(match, ignore.case = TRUE, vars = peek_vars())
ends_with(match, ignore.case = TRUE, vars = peek_vars())
contains(match, ignore.case = TRUE, vars = peek_vars())
matches(match, ignore.case = TRUE, perl = FALSE, vars = peek_vars())
num_range(prefix, range, width = NULL, vars = peek_vars())
all_of(x, vars = peek_vars())
any_of(x, vars = peek_vars())
everything(vars = peek_vars())
last_col(offset = 0L, vars = peek_vars())

Value

An integer vector giving the position of the matched variables.

Arguments

match

character(n). If length > 1, the union of the matches is taken.

ignore.case

logical(1). If TRUE, the default, ignores case when matching names.

vars

character(n). A character vector of variable names. When called from inside selecting functions such as select(), these are automatically set to the names of the table.

perl

logical(1). Should Perl-compatible regexps be used?

prefix

A prefix which starts the numeric range.

range

integer(n). A sequence of integers, e.g. 1:5.

width

numeric(1). Optionally, the "width" of the numeric range. For example, a range of 2 gives "01", a range of three "001", etc.

x

character(n). A vector of column names.

offset

integer(1). Select the nth variable from the end of the data.frame.

See Also

select(), relocate(), where(), group_cols()

Examples

mtcars %>% select(starts_with("c"))
mtcars %>% select(starts_with(c("c", "h")))
mtcars %>% select(ends_with("b"))
mtcars %>% relocate(contains("a"), .before = mpg)
iris %>% select(matches(".t."))
mtcars %>% select(last_col())

# `all_of()` selects the variables in a character vector:
iris %>% select(all_of(c("Petal.Length", "Petal.Width")))
# `all_of()` is strict and will throw an error if the column name isn't found
try({iris %>% select(all_of(c("Species", "Genres")))})
# However `any_of()` allows missing variables
iris %>% select(any_of(c("Species", "Genres")))