为什么“一个" < R中等于2 FALSE? [英] Why does "one" < 2 equal FALSE in R?

问题描述

我正在阅读Hadley Wickham的有关胁迫的Advanced R部分，但我无法理解此比较的结果:

I'm reading Hadley Wickham's Advanced R section on coercion, and I can't understand the result of this comparison:

"one" < 2
# [1] FALSE

我假设R将2强制转换为字符，但是我不明白为什么R返回FALSE而不是返回错误.自此以来，这尤其让我感到困惑.

I'm assuming that R coerces 2 to a character, but I don't understand why R returns FALSE instead of returning an error. This is especially puzzling to me since

-1 < "one"
# TRUE

所以我的问题有两个:首先，为什么要回答这个问题，其次，有没有办法看到R如何像这些示例一样在逻辑向量中转换单个元素?

So my question is two-fold: first, why this answer, and second, is there a way of seeing how R converts the individual elements within a logical vector like these examples?

推荐答案

来自help("<"):

如果两个参数是不同类型的原子向量，则一个是 强迫其他类型，优先级(递减) 是字符，复杂，数字，整数，逻辑和原始.

If the two arguments are atomic vectors of different types, one is coerced to the type of the other, the (decreasing) order of precedence being character, complex, numeric, integer, logical and raw.

因此，在这种情况下，数字的优先级低于字符.因此，2被强制为字符"2".字符向量中字符串的比较是按字典顺序进行的，据我所知，它是按字母顺序排列的，但与语言环境有关.

So in this case, the numeric is of lower precedence than the character. So 2 is coerced to the character "2". Comparison of strings in character vectors is lexicographic which, as I understand it, is alphabetic but locale-dependent.

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