dplyr::select() 带有一些可能不存在于数据框中的变量? [英] dplyr::select() with some variables that may not exist in the data frame?

问题描述

我有一个辅助函数(比如 foo())，它将在各种可能包含或不包含指定变量的数据帧上运行.假设我有

I have a helper function (say foo()) that will be run on various data frames that may or may not contain specified variables. Suppose I have

library(dplyr)
d1 <- data_frame(taxon=1,model=2,z=3)
d2 <- data_frame(taxon=2,pss=4,z=3)

我要选择的变量是

vars <- intersect(names(data),c("taxon","model","z"))

也就是说，我希望 foo(d1) 返回 taxon、model 和 z> 列，而 foo(d2) 只返回 taxon 和 z.

that is, I'd like foo(d1) to return the taxon, model, and z columns, while foo(d2) returns just taxon and z.

如果 foo 包含 select(data,c(taxon,model,z)) 那么 foo(d2) 失败(因为 d2 不包含 model).如果我使用 select(data,-pss) 那么 foo(d1) 同样失败.

If foo contains select(data,c(taxon,model,z)) then foo(d2) fails (because d2 doesn't contain model). If I use select(data,-pss) then foo(d1) fails similarly.

如果我退出 tidyverse，我知道如何执行此操作(只需返回 data[vars])，但我想知道是否有一种方便的方法来执行此操作 (1)select() 某种类型的助手 (tidyselect::select_helpers) 或 (2) 与 tidyeval(我仍然还没有找到时间把我的头转过来！)

I know how to do this if I retreat from the tidyverse (just return data[vars]), but I'm wondering if there's a handy way to do this either (1) with a select() helper of some sort (tidyselect::select_helpers) or (2) with tidyeval (which I still haven't found time to get my head around!)

推荐答案

另一个选项是 select_if:

d2 %>% select_if(names(.) %in% c('taxon', 'model', 'z'))

# # A tibble: 1 x 2
#   taxon     z
#   <dbl> <dbl>
# 1     2     3

---

select_if 被取代.使用 any_of 代替:

---

select_if is superseded. Use any_of instead:

d2 %>% select(any_of(c('taxon', 'model', 'z')))
# # A tibble: 1 x 2
#   taxon     z
#   <dbl> <dbl>
# 1     2     3

在 R 中输入 ?dplyr::select 你会发现:

type ?dplyr::select in R and you will find this:

这些助手从字符向量中选择变量:

These helpers select variables from a character vector:

all_of():匹配字符向量中的变量名.所有名字都必须存在，否则抛出越界错误.

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

any_of():与 all_of() 相同，只是不为名称抛出错误不存在的.

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

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