R: Select helpers

select_helpers {tidyselect} | R Documentation

## 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

- `num_range()`: a numerical range like x01, x02, x03.

- `one_of()`: variables in character vector.

- `everything()`: all variables.

- `last_col()`: 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, vars = peek_vars())

    num_range(prefix, range, width = NULL, vars = peek_vars())

    one_of(..., .vars = peek_vars())

    everything(vars = peek_vars())

    last_col(offset = 0L, vars = peek_vars())

### Arguments

`match` | A string.
`ignore.case` | If `TRUE`, the default, ignores case when matching names.
`vars, .vars` | A character vector of variable names. When called from inside selecting functions like `dplyr::select()` these are automatically set to the names of the table.
`prefix` | A prefix that starts the numeric range.
`range` | A sequence of integers, like `1:5`
`width` | Optionally, the "width" of the numeric range. For example, a range of 2 gives "01", a range of three "001", etc.
`...` | One or more character vectors.
`offset` | Set it to `n` to select the nth var from the end.

### Value

An integer vector giving the position of the matched variables.

### Examples

    nms <- names(iris)
    vars_select(nms, starts_with("Petal"))
    vars_select(nms, ends_with("Width"))
    vars_select(nms, contains("etal"))
    vars_select(nms, matches(".t."))
    vars_select(nms, Petal.Length, Petal.Width)
    vars_select(nms, everything())
    vars_select(nms, last_col())
    vars_select(nms, last_col(offset = 2))

    vars <- c("Petal.Length", "Petal.Width")
    vars_select(nms, one_of(vars))

[Package tidyselect version 0.2.4 Index]