R - 如何在 IF 语句中测试字符(0) [英] R - How to test for character(0) in IF statement

问题描述

我想这非常简单，但我似乎找不到答案.

I imagine this is incredibly simple but I cant seem to find the answer.

我正在编写 IF 语句，但测试的是对象是否返回 character(0) 值.我不知道如何处理语句中的 character(0).

I am writing an IF statement but the test is if the object returns a character(0) value. I am not sure how to deal with character(0) in the statement.

假设 Test <- character(0) 或一个值:

if (identical(Pols4,character(0))) {
  print('Empty')
} else {
  print('Not Empty')
}

好像还是不行.....

It still does not seem to work.....

推荐答案

使用 identical 函数来检查这个.

Use the identical function to check this.

a <- character(0)
identical(a, character(0))  # returns TRUE

identical(a, "")           # returns FALSE
identical(a, numeric(0))   # returns also FALSE

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