在 R 中按分隔符拆分字符串
本文将讨论如何在 R 中通过分隔符分割字符串。
在 R 中使用 strsplit 按分隔符拆分字符串
strsplit 随 R 基础库一起提供，应该可以在大多数安装中使用而无需额外的包。strsplit 通过给定的分隔符将字符向量拆分为子字符串，该分隔符也提供了一个字符向量。该函数的第一个参数是要拆分的字符向量。在这种情况下，我们指定空格字符来分隔给定句子中的每个单词。请注意，输出是作为字符向量列表给出的。
library(dplyr)
library(stringr)
str <- "Lorem Ipsum is simply dummied text of the printing and typesetting industry."
strsplit(str, " ")
输出：
> strsplit(str, " ")
[[1]]
[1] "Lorem" "Ipsum" "is" "simply" "dummied" "text"
[7] "of" "the" "printing" "and" "typesetting" "industry."
在 R 中使用 str_split 按分隔符拆分字符串
或者，str_split 函数也可用于按分隔符拆分字符串。str_split 是 stringr 包的一部分。它的工作方式几乎与 strsplit 相同，除了 str_split 还采用正则表达式作为模式。在下面的例子中，我们只传递固定字符串进行匹配。请注意，该函数可以选择采用第三个参数，该参数表示要返回的子字符串的数量。
library(dplyr)
library(stringr)
str <- "Lorem Ipsum is simply dummied text of the printing and typesetting industry."
str_split(str, " ")
输出：
> str_split(str, " ")
[[1]]
[1] "Lorem" "Ipsum" "is" "simply" "dummied" "text"
[7] "of" "the" "printing" "and" "typesetting" "industry."
str_split 函数中的另一个可选参数是 simplify，它排在第四位。默认情况下，此参数的值为 FALSE，这会强制函数将子字符串作为字符向量列表返回。如果我们将 TRUE 分配给给定的参数，str_split 将返回一个字符矩阵。
library(dplyr)
library(stringr)
fruits <- c(
"apples and oranges and pears and bananas",
"pineapples and mangos and raspberries"
)
str_split(fruits, " and ")
str_split(fruits, " and ", simplify = TRUE)
输出：
> str_split(fruits, " and ")
[[1]]
[1] "apples" "oranges" "pears" "bananas"
[[2]]
[1] "pineapples" "mangos" "raspberries"
> str_split(fruits, " and ", simplify = TRUE)
[,1] [,2] [,3] [,4]
[1,] "apples" "oranges" "pears" "bananas"
[2,] "pineapples" "mangos" "raspberries" ""
Founder of DelftStack.com. Jinku has worked in the robotics and automotive industries for over 8 years. He sharpened his coding skills when he needed to do the automatic testing, data collection from remote servers and report creation from the endurance test. He is from an electrical/electronics engineering background but has expanded his interest to embedded electronics, embedded programming and front-/back-end programming.
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