R语言 dplyr selec 辅助函数

Tidyverse selections implement a dialect of R where operators make it easy to select variables:

: for selecting a range of consecutive variables.

! for taking the complement of a set of variables.

& and | for selecting the intersection or the union of two sets of variables.

c() for combining selections.

In addition, you can use selection helpers such as:

everything(): Matches all variables.

last_col(): Select last variable, possibly with an offset.

These helpers select variables based on their names:

starts_with(): Starts with a prefix.

ends_with(): Ends with a suffix.

contains(): Contains a literal string.

matches(): Matches a regular expression.

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

These functions select variables from a character vector.

all_of(): Matches variable names in a character vector. All names must be present, otherwise an out-of-bounds error is thrown.

any_of(): Same as all_of(), except that no error is thrown for names that don't exist.

select使用变量作为参数的时候会警告，select(var_vector)的正确写法应该是select(all_of(var_vector))，因为可能出现 var_vector这个变量名本身是column name的情况。