字符（）和“”之间的差异在R [英] Differences between character() and "" in R

问题描述

只是意识到输出是不同的：

Just realize the output is different:

> y=""
> y
[1] ""
> y=character()
> y
character(0)

但是，没有什么奇怪的事情发生了。我不清楚这些差异，并希望保持这个问题（如果有的话）清楚。

However, nothing odd has happened. And I am not clear about these differences, and want to keep this problem(if any) clear in mind. So, thank you for helping.

推荐答案

您会混淆向量的长度（元素数）与字符数在字符串中：

You are confusing the length (number of elements) of a vector with the number of characters in a string:

考虑以下三件事：

> x=c("","")
> y=""
> z=character()

它们的长度是向量中的元素数量：

Their length is the number of elements in the vector:

> length(x)
[1] 2
> length(y)
[1] 1
> length(z)
[1] 0

要获得字符数， code> nchar ：

To get the number of characters, use nchar:

> nchar(x)
[1] 0 0
> nchar(y)
[1] 0
> nchar(z)
integer(0)

$ b （x）显示 x 的每个元素中有多少个字母，因此返回两个零的整数向量。 nchar（y）则是一个零的整数向量。

Note that nchar(x) shows how many letters in each element of x, so it returns an integer vector of two zeroes. nchar(y) is then an integer vector of one zero.

所以最后一个， nchar（z）返回 integer（0），这是一个无零的整数向量。它的长度为零。它没有元素，但如果它有元素，它们将是整数。

So the last one, nchar(z) returns an integer(0), which is an integer vector of no zeroes. It has length of zero. It has no elements, but if it did have elements, they would be integers.

字符（0）是字符类型对象的空向量。比较：

character(0) is an empty vector of character-type objects. Compare:

> character(0)
character(0)
> character(1)
[1] ""
> character(2)
[1] "" ""
> character(12)
[1] "" "" "" "" "" "" "" "" "" "" "" ""

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