如何在R中动态选择数据框中的列[重复]

Question

我想在tibble 中选择名为“b”的列。 “b”是名为col_name 的变量的值。

library(dplyr)
#> 
#> Attaching package: 'dplyr'
#> The following objects are masked from 'package:stats':
#> 
#>     filter, lag
#> The following objects are masked from 'package:base':
#> 
#>     intersect, setdiff, setequal, union
col_name <- "b" # the column to select

df <- tibble(a = c(1,2,3), b = c(2,4,6))

df$b
#> [1] 2 4 6
# But I want to use a variable to dynamically select the column
df$col_name
#> Warning: Unknown or uninitialised column: `col_name`.
#> NULL
Created on 2020-10-12 by the reprex package (v0.3.0)

Answer 1

df %>% select( {{ col_name }} )
#or
df %>% select( !!col_name )
#or
df[[col_name]]

在最后一种情况下，您将获得一个向量而不是数据框