根据多个属性条件选择列 [英] Select columns based on multiple attribute conditions

问题描述

我试图弄清楚如何使用 dplyr :: select_if 有效地选择列。 dplyr 0.70中的 starwars 数据集可用于此目的：

I am trying to figure how to efficiently select columns using dplyr::select_if. The starwars data set in dplyr 0.70 is a good dataset to use for this:

> starwars
# A tibble: 87 x 13
                 name height  mass    hair_color  skin_color eye_color birth_year gender homeworld species     films  vehicles starships
                <chr>  <int> <dbl>         <chr>       <chr>     <chr>      <dbl>  <chr>     <chr>   <chr>    <list>    <list>    <list>
 1     Luke Skywalker    172    77         blond        fair      blue       19.0   male  Tatooine   Human <chr [5]> <chr [2]> <chr [2]>
 2              C-3PO    167    75          <NA>        gold    yellow      112.0   <NA>  Tatooine   Droid <chr [6]> <chr [0]> <chr [0]>
 3              R2-D2     96    32          <NA> white, blue       red       33.0   <NA>     Naboo   Droid <chr [7]> <chr [0]> <chr [0]>
 4        Darth Vader    202   136          none       white    yellow       41.9   male  Tatooine   Human <chr [4]> <chr [0]> <chr [1]>
 5        Leia Organa    150    49         brown       light     brown       19.0 female  Alderaan   Human <chr [5]> <chr [1]> <chr [0]>
 6          Owen Lars    178   120   brown, grey       light      blue       52.0   male  Tatooine   Human <chr [3]> <chr [0]> <chr [0]>
 7 Beru Whitesun lars    165    75         brown       light      blue       47.0 female  Tatooine   Human <chr [3]> <chr [0]> <chr [0]>
 8              R5-D4     97    32          <NA>  white, red       red         NA   <NA>  Tatooine   Droid <chr [1]> <chr [0]> <chr [0]>
 9  Biggs Darklighter    183    84         black       light     brown       24.0   male  Tatooine   Human <chr [1]> <chr [0]> <chr [1]>
10     Obi-Wan Kenobi    182    77 auburn, white        fair blue-gray       57.0   male   Stewjon   Human <chr [6]> <chr [1]> <chr [5]>

现在说我想选择仅是整数的列。效果很好：

Now say that I would like select columns that are only integers. This works well:

library(dplyr)

starwars %>%
  select_if(is.numeric)

但是，如果我想基于多个条件进行选择，该怎么办。例如，也许我想要数字和字符列：

But what should I do if I want to select based on multiple criteria. For example maybe I want both numeric and character columns:

starwars %>%
  select_if(c(is.numeric, is.character))

或者也许我想要所有数字和名称列：

Or maybe I want all numeric AND the name column:

starwars %>%
  select_if(name, is.character)

以上两个示例都不起作用，所以我想知道如何完成我概述的内容

Neither of the two examples above work so I am wondering how I might accomplish what I've outlined here.

推荐答案

优雅的tidyverse语法，其中〜代表匿名函数，在使用 select_if 函数时会有所帮助：

Elegant tidyverse syntax where ~ stands for anonymous function may be helpful when using select_if function:

require(tidyverse)

# numeric and character columns
starwars %>% select_if(~ is.numeric(.) | is.character(.)) 

# all numeric AND the name column
starwars %>% select(name, where(is.numeric))

谓词函数，例如建议出于某些原因在 select 内的 is.numeric 应当包装在 where（）中据tidyverse创作者。

Predicate functions e.g. is.numeric inside of select for some reason is recommended to be wrapped in where() according to tidyverse creators.

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