File: select.Rd

package info (click to toggle)
r-cran-dplyr 1.1.4-4
  • links: PTS, VCS
  • area: main
  • in suites: forky, sid, trixie
  • size: 4,292 kB
  • sloc: cpp: 1,403; sh: 17; makefile: 7
file content (254 lines) | stat: -rw-r--r-- 9,140 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
150
151
152
153
154
155
156
157
158
159
160
161
162
163
164
165
166
167
168
169
170
171
172
173
174
175
176
177
178
179
180
181
182
183
184
185
186
187
188
189
190
191
192
193
194
195
196
197
198
199
200
201
202
203
204
205
206
207
208
209
210
211
212
213
214
215
216
217
218
219
220
221
222
223
224
225
226
227
228
229
230
231
232
233
234
235
236
237
238
239
240
241
242
243
244
245
246
247
248
249
250
251
252
253
254
% Generated by roxygen2: do not edit by hand
% Please edit documentation in R/select.R
\name{select}
\alias{select}
\title{Keep or drop columns using their names and types}
\usage{
select(.data, ...)
}
\arguments{
\item{.data}{A data frame, data frame extension (e.g. a tibble), or a
lazy data frame (e.g. from dbplyr or dtplyr). See \emph{Methods}, below, for
more details.}

\item{...}{<\code{\link[=dplyr_tidy_select]{tidy-select}}> One or more unquoted
expressions separated by commas. Variable names can be used as if they
were positions in the data frame, so expressions like \code{x:y} can
be used to select a range of variables.}
}
\value{
An object of the same type as \code{.data}. The output has the following
properties:
\itemize{
\item Rows are not affected.
\item Output columns are a subset of input columns, potentially with a different
order. Columns will be renamed if \code{new_name = old_name} form is used.
\item Data frame attributes are preserved.
\item Groups are maintained; you can't select off grouping variables.
}
}
\description{
Select (and optionally rename) variables in a data frame, using a concise
mini-language that makes it easy to refer to variables based on their name
(e.g. \code{a:f} selects all columns from \code{a} on the left to \code{f} on the
right) or type (e.g. \code{where(is.numeric)} selects all numeric columns).
\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:everything]{last_col()}}: Select last variable, possibly with an offset.
\item \code{\link[=group_cols]{group_cols()}}: Select all grouping columns.
}

Other 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:starts_with]{ends_with()}}: Ends with a suffix.
\item \code{\link[tidyselect:starts_with]{contains()}}: Contains a literal string.
\item \code{\link[tidyselect:starts_with]{matches()}}: Matches a regular expression.
\item \code{\link[tidyselect:starts_with]{num_range()}}: Matches a numerical range like x01, x02, x03.
}

Or from variables stored in 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:all_of]{any_of()}}: Same as \code{all_of()}, except that no error is thrown
for names that don't exist.
}

Or using a predicate 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{Methods}{

This function is a \strong{generic}, which means that packages can provide
implementations (methods) for other classes. See the documentation of
individual methods for extra arguments and differences in behaviour.

The following methods are currently available in loaded packages:
\Sexpr[stage=render,results=rd]{dplyr:::methods_rd("select")}.
}

\section{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="sourceCode r">}}\preformatted{library(tidyverse)

# For better printing
iris <- as_tibble(iris)
}\if{html}{\out{</div>}}

Select variables by name:

\if{html}{\out{<div class="sourceCode r">}}\preformatted{starwars \%>\% select(height)
#> # A tibble: 87 x 1
#>   height
#>    <int>
#> 1    172
#> 2    167
#> 3     96
#> 4    202
#> # i 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
#> # i 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="sourceCode 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
#> # i 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="sourceCode 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
#> # i 296 more rows
}\if{html}{\out{</div>}}
\subsection{Operators:}{

The \code{:} operator selects a range of consecutive variables:

\if{html}{\out{<div class="sourceCode 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
#> # i 83 more rows
}\if{html}{\out{</div>}}

The \code{!} operator negates a selection:

\if{html}{\out{<div class="sourceCode 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  masculine Tatooine  Human  
#> 2 <NA>       gold        yellow         112   none  masculine Tatooine  Droid  
#> 3 <NA>       white, blue red             33   none  masculine Naboo     Droid  
#> 4 none       white       yellow          41.9 male  masculine Tatooine  Human  
#> # i 83 more rows
#> # i 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 
#> # i 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 
#> # i 146 more rows
}\if{html}{\out{</div>}}

\code{&} and \code{|} take the intersection or the union of two selections:

\if{html}{\out{<div class="sourceCode 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
#> # i 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
#> # i 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="sourceCode 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
#> # i 146 more rows
}\if{html}{\out{</div>}}
}
}

\seealso{
Other single table verbs: 
\code{\link{arrange}()},
\code{\link{filter}()},
\code{\link{mutate}()},
\code{\link{reframe}()},
\code{\link{rename}()},
\code{\link{slice}()},
\code{\link{summarise}()}
}
\concept{single table verbs}