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法律如何在 R 中從字串中提取第一個、最後一個或中間字元？
在文字分析中，我們可能需要從一個字串中提取字元，或者從向量的字串中提取字元。此提取可能需要建立一個字串，其中包含用於進一步分析的某些特定單詞。藉助 stringr 包的 str_sub 函式，我們可以做到這一點。
示例
考慮以下字串 -
> x1<-"Removing harmful things from the road is an act of charity"
載入 stringr 包 -
> library(stringr) > str_sub(x1,1,8) [1] "Removing" > str_sub(x1,1,23) [1] "Removing harmful things" > str_sub(x1,29,37) [1] " the road" > str_sub(x1,30,37) [1] "the road" > str_sub(x1,-58,-51) [1] "Removing" > str_sub(x1,-58,-1) [1] "Removing harmful things from the road is an act of charity" > str_sub(x1,-7,-1) [1] "charity" > str_sub(x1,-14,-1) [1] "act of charity" > str_sub(x1,-17,-1) [1] "an act of charity"
讓我們來看看對向量的字串數的提取 -
> x1<-c("Removing", "harmful", "things", "from", "the", "road", "is", "an", "act", "of", "charity")
> str_sub(x1,1,2)
[1] "Re" "ha" "th" "fr" "th" "ro" "is" "an" "ac" "of" "ch"
> str_sub(x1,1,3)
[1] "Rem" "har" "thi" "fro" "the" "roa" "is" "an" "act" "of" "cha"
> str_sub(x1,1,10)
[1] "Removing" "harmful" "things" "from" "the" "road"
[7] "is" "an" "act" "of" "charity"
> str_sub(x1,-7,-2)
[1] "emovin" "harmfu" "thing" "fro" "th" "roa" "i" "a"
[9] "ac" "o" "charit"
> str_sub(x1,-7,-1)
[1] "emoving" "harmful" "things" "from" "the" "road" "is"
[8] "an" "act" "of" "charity"
> str_sub(x1,-10,-1)
[1] "Removing" "harmful" "things" "from" "the" "road"
[7] "is" "an" "act" "of" "charity"
更新於: 11-Aug-2020
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