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% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/helpers.R
\name{language}
\alias{language}
\alias{select_helpers}
\title{Selection language}
\description{
\subsection{Overview of selection features:}{
Tidyverse selections implement a dialect of R where operators make
it easy to select variables:
\itemize{
\item \code{:} for selecting a range of consecutive variables.
\item \code{!} for taking the complement of a set of variables.
\item \code{&} and \code{|} for selecting the intersection or the union of two
sets of variables.
\item \code{c()} for combining selections.
}
In addition, you can use \strong{selection helpers}. Some helpers select specific
columns:
\itemize{
\item \code{\link[tidyselect:everything]{everything()}}: Matches all variables.
\item \code{\link[tidyselect:last_col]{last_col()}}: Select last variable, possibly with an offset.
}
These helpers select variables by matching patterns in their names:
\itemize{
\item \code{\link[tidyselect:starts_with]{starts_with()}}: Starts with a prefix.
\item \code{\link[tidyselect:ends_with]{ends_with()}}: Ends with a suffix.
\item \code{\link[tidyselect:contains]{contains()}}: Contains a literal string.
\item \code{\link[tidyselect:matches]{matches()}}: Matches a regular expression.
\item \code{\link[tidyselect:num_range]{num_range()}}: Matches a numerical range like x01, x02, x03.
}
These helpers select variables from a character vector:
\itemize{
\item \code{\link[tidyselect:all_of]{all_of()}}: Matches variable names in a character vector. All
names must be present, otherwise an out-of-bounds error is
thrown.
\item \code{\link[tidyselect:any_of]{any_of()}}: Same as \code{all_of()}, except that no error is thrown
for names that don't exist.
}
This helper selects variables with a function:
\itemize{
\item \code{\link[tidyselect:where]{where()}}: Applies a function to all variables and selects those
for which the function returns \code{TRUE}.
}
}
}
\section{Simple examples}{
Here we show the usage for the basic selection operators. See the
specific help pages to learn about helpers like \code{\link[=starts_with]{starts_with()}}.
The selection language can be used in functions like
\code{dplyr::select()} or \code{tidyr::pivot_longer()}. Let's first attach
the tidyverse:\if{html}{\out{<div class="r">}}\preformatted{library(tidyverse)
# For better printing
iris <- as_tibble(iris)
}\if{html}{\out{</div>}}
Select variables by name:\if{html}{\out{<div class="r">}}\preformatted{starwars \%>\% select(height)
#> # A tibble: 87 x 1
#> height
#> <int>
#> 1 172
#> 2 167
#> 3 96
#> 4 202
#> # ... with 83 more rows
iris \%>\% pivot_longer(Sepal.Length)
#> # A tibble: 150 x 6
#> Sepal.Width Petal.Length Petal.Width Species name value
#> <dbl> <dbl> <dbl> <fct> <chr> <dbl>
#> 1 3.5 1.4 0.2 setosa Sepal.Length 5.1
#> 2 3 1.4 0.2 setosa Sepal.Length 4.9
#> 3 3.2 1.3 0.2 setosa Sepal.Length 4.7
#> 4 3.1 1.5 0.2 setosa Sepal.Length 4.6
#> # ... with 146 more rows
}\if{html}{\out{</div>}}
Select multiple variables by separating them with commas. Note how
the order of columns is determined by the order of inputs:\if{html}{\out{<div class="r">}}\preformatted{starwars \%>\% select(homeworld, height, mass)
#> # A tibble: 87 x 3
#> homeworld height mass
#> <chr> <int> <dbl>
#> 1 Tatooine 172 77
#> 2 Tatooine 167 75
#> 3 Naboo 96 32
#> 4 Tatooine 202 136
#> # ... with 83 more rows
}\if{html}{\out{</div>}}
Functions like \code{tidyr::pivot_longer()} don't take variables with
dots. In this case use \code{c()} to select multiple variables:\if{html}{\out{<div class="r">}}\preformatted{iris \%>\% pivot_longer(c(Sepal.Length, Petal.Length))
#> # A tibble: 300 x 5
#> Sepal.Width Petal.Width Species name value
#> <dbl> <dbl> <fct> <chr> <dbl>
#> 1 3.5 0.2 setosa Sepal.Length 5.1
#> 2 3.5 0.2 setosa Petal.Length 1.4
#> 3 3 0.2 setosa Sepal.Length 4.9
#> 4 3 0.2 setosa Petal.Length 1.4
#> # ... with 296 more rows
}\if{html}{\out{</div>}}
\subsection{Operators:}{
The \code{:} operator selects a range of consecutive variables:\if{html}{\out{<div class="r">}}\preformatted{starwars \%>\% select(name:mass)
#> # A tibble: 87 x 3
#> name height mass
#> <chr> <int> <dbl>
#> 1 Luke Skywalker 172 77
#> 2 C-3PO 167 75
#> 3 R2-D2 96 32
#> 4 Darth Vader 202 136
#> # ... with 83 more rows
}\if{html}{\out{</div>}}
The \code{!} operator negates a selection:\if{html}{\out{<div class="r">}}\preformatted{starwars \%>\% select(!(name:mass))
#> # A tibble: 87 x 11
#> hair_color skin_color eye_color birth_year sex gender homeworld species
#> <chr> <chr> <chr> <dbl> <chr> <chr> <chr> <chr>
#> 1 blond fair blue 19 male mascu~ Tatooine Human
#> 2 <NA> gold yellow 112 none mascu~ Tatooine Droid
#> 3 <NA> white, bl~ red 33 none mascu~ Naboo Droid
#> 4 none white yellow 41.9 male mascu~ Tatooine Human
#> # ... with 83 more rows, and 3 more variables: films <list>, vehicles <list>,
#> # starships <list>
iris \%>\% select(!c(Sepal.Length, Petal.Length))
#> # A tibble: 150 x 3
#> Sepal.Width Petal.Width Species
#> <dbl> <dbl> <fct>
#> 1 3.5 0.2 setosa
#> 2 3 0.2 setosa
#> 3 3.2 0.2 setosa
#> 4 3.1 0.2 setosa
#> # ... with 146 more rows
iris \%>\% select(!ends_with("Width"))
#> # A tibble: 150 x 3
#> Sepal.Length Petal.Length Species
#> <dbl> <dbl> <fct>
#> 1 5.1 1.4 setosa
#> 2 4.9 1.4 setosa
#> 3 4.7 1.3 setosa
#> 4 4.6 1.5 setosa
#> # ... with 146 more rows
}\if{html}{\out{</div>}}
\code{&} and \code{|} take the intersection or the union of two selections:\if{html}{\out{<div class="r">}}\preformatted{iris \%>\% select(starts_with("Petal") & ends_with("Width"))
#> # A tibble: 150 x 1
#> Petal.Width
#> <dbl>
#> 1 0.2
#> 2 0.2
#> 3 0.2
#> 4 0.2
#> # ... with 146 more rows
iris \%>\% select(starts_with("Petal") | ends_with("Width"))
#> # A tibble: 150 x 3
#> Petal.Length Petal.Width Sepal.Width
#> <dbl> <dbl> <dbl>
#> 1 1.4 0.2 3.5
#> 2 1.4 0.2 3
#> 3 1.3 0.2 3.2
#> 4 1.5 0.2 3.1
#> # ... with 146 more rows
}\if{html}{\out{</div>}}
To take the difference between two selections, combine the \code{&} and
\code{!} operators:\if{html}{\out{<div class="r">}}\preformatted{iris \%>\% select(starts_with("Petal") & !ends_with("Width"))
#> # A tibble: 150 x 1
#> Petal.Length
#> <dbl>
#> 1 1.4
#> 2 1.4
#> 3 1.3
#> 4 1.5
#> # ... with 146 more rows
}\if{html}{\out{</div>}}
}
}
\section{Details}{
The order of selected columns is determined by the inputs.
\itemize{
\item \code{all_of(c("foo", "bar"))} selects \code{"foo"} first.
\item \code{c(starts_with("c"), starts_with("d"))} selects all columns
starting with \code{"c"} first, then all columns starting with \code{"d"}.
}
}
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