具有NA，TRUE和FALSE的逻辑运算符(AND，OR) [英] Logical operators (AND, OR) with NA, TRUE and FALSE

问题描述

当与逻辑OR(|)和逻辑AND(&)一起使用时，我无法理解逻辑(布尔)值TRUE，FALSE和NA的属性.以下是一些示例:

I cannot understand the properties of logical (boolean) values TRUE, FALSE and NA when used with logical OR (|) and logical AND (&). Here are some examples:

NA | TRUE
# [1] TRUE

NA | FALSE
# [1] NA

NA & TRUE
# [1] NA

NA & FALSE
# [1] FALSE

您能解释这些输出吗?

推荐答案

引用?Logic:

NA是有效的逻辑对象.如果x或y的分量为NA，则 如果结果不明确，则结果为NA.换句话说，NA&N. TRUE表示NA，但NA& FALSE评估为FALSE.见 下面的示例.

NA is a valid logical object. Where a component of x or y is NA, the result will be NA if the outcome is ambiguous. In other words NA & TRUE evaluates to NA, but NA & FALSE evaluates to FALSE. See the examples below.

其中的关键是模糊"一词. NA表示未知".因此NA & TRUE可以为true或false，但我们不知道.而NA & FALSE将为假，无论缺失值是什么.

The key there is the word "ambiguous". NA represents something that is "unknown". So NA & TRUE could be either true or false, but we don't know. Whereas NA & FALSE will be false no matter what the missing value is.

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