为什么one_of（）会调用它？-Whyisone_of()calledthat?

9  

one_of allows for guessing or subset-matching

one_of允许猜测或子集匹配

Let's say I know in general my column names will come from c("mpg","cyl","garbage") but I don't know which columns will be present because of interactivity/reactivity

假设我一般都知道我的列名将来自c(“mpg”,“cyl”,“garbage”)但我不知道由于交互性/反应性会出现哪些列

mtcars %>% select(one_of(c("mpg","cyl","garbage")))

evaluates but provides a message

评估但提供信息

Warning message:
Unknown variables: `garbage`

In contrast

mtcars %>% select(mpg, cyl, garbage)

does not evaluate and gives the error

不评估并给出错误

Error in overscope_eval_next(overscope, expr) : 
  object 'garbage' not found    

8  

The way I think about it is that select() eventually evaluates to a logical vector. So if you use starts_with it goes through the variables in the dataframe and asks whether the variable name starts with the right set of characters. one_of does the same thing but asks whether the variable name is one of the names listed in the character vector. But as they say, naming things is hard!

我想到的方式是select()最终评估为逻辑向量。因此,如果您使用starts_with,它将遍历数据框中的变量,并询问变量名称是否以正确的字符集开头。 one_of做同样的事情,但询问变量名是否是字符向量中列出的名称之一。但正如他们所说,命名事情很难!