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Legal Studies如何在 R 中從字串中提取前兩個字元？
字串可以很短也可以很長，我們也可以在 R 中同時擁有一個向量或字串列表。當我們想將字串用於單個或多個比較時，通常會提取部分字串。如果我們要從字串中提取前兩個字元，我們可以使用子字串函式，語法為 substr(“String_object Or String”,start=1,stop=2)
示例
x1<-"Tutorialspoint"
substr(x1,start=1,stop=2)
[1] "Tu"
x2<-"Programing"
substr(x2,start=1,stop=2)
[1] "Pr"
x3<-"R-Programming"
substr(x3,start=1,stop=2)
[1] "R-"
x4<-"R<>Programming"
substr(x4,start=1,stop=2)
[1] "R<"
x5<-"R!Programming"
substr(x5,start=1,stop=2)
[1] "R!"
x6<-"R/Programming"
substr(x6,start=1,stop=2)
[1] "R/"
x7<-"R@Programming"
substr(x7,start=1,stop=2)
[1] "R@"
x8<-"R~Programming"
substr(x8,start=1,stop=2)
[1] "R~"
x9<-"VALANY"
substr(x9,start=1,stop=2)
[1] "VA"
x10<-"1 to 10"
substr(x10,start=1,stop=2)
[1] "1 "
x11<-"10 to 20"
substr(x11,start=1,stop=2)
[1] "10"
x12<-"North to South"
substr(x12,start=1,stop=2)
[1] "No"
x13<-"No to Yes"
substr(x13,start=1,stop=2)
[1] "No"
x14<-"1.5 and 2.5"
substr(x14,start=1,stop=2)
[1] "1."
x15<-c("AB","CD","EF","GH","IJ")
substr(x15,start=1,stop=2)
[1] "AB" "CD" "EF" "GH" "IJ"
x16<-c("ABCD","EFGH","IJKL")
substr(x16,start=1,stop=2)
[1] "AB" "EF" "IJ"
更新於：24-8-2020
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