R语言中sub函数的用法

 

1、

> sub("b", "x", c("abbc", "bbcd", "cde"))      ## 三个字符串中第一个“b”被替换为了“x”
[1] "axbc" "xbcd" "cde" 

 

> gsub("b", "x", c("abbc", "bbcd", "cde"))     ##gsub中的g表示全局， 即所有的“b”都被替换为了“x”
[1] "axxc" "xxcd" "cde" 

 

2、sub/gsub可以应用正则

> sub("^a","x",c("abcd","dcba"))     ##^a表示开头的a， 即开头的a被替换为x
[1] "xbcd" "dcba"

 

> sub("a$","x",c("abcd","dcba"))     ##a$表示结尾的a， 即结尾的a被替换为x
[1] "abcd" "dcbx"

 

> sub("a.c","x",c("abcd","sdacd"))   ##.表示任一个，即abc被替换为x
[1] "xd"    "sdacd"

 

> sub("a*b","x",c("aabcd","dcaaaba"))   ## *表示将前面的一个字符匹配0个至任意多个，即aab和aaab同时被替换为了x
[1] "xcd"  "dcxa"

 

> sub("a.*e","x",c("abcde","edcba"))   ## 将a及其后任意字符1次至多次至e替换为x， 即将abcde替换为x
[1] "x"     "edcba"
> sub("a*e","x",c("abcde","edcba"))    ## 将0个至多个a到e的字符替换为x，即将e替换为了x
[1] "abcdx" "xdcba"

 

> sub("ab|ba","x",c("abcd","dcba"))    ##将ab或者ba替换我x
[1] "xcd" "dcx"

 

> sub("[^ab]","x",c("abcd","dcba"))    ## 将非ab的字符替换为x，只替换第一个
[1] "abxd" "xcba"
> gsub("[^ab]","x",c("abcd","dcba"))   ## g表示全局
[1] "abxx" "xxba"

 

> sub("[ab]","x",c("abcd","dcba"))    ## 将a和b替换为x
[1] "xbcd" "dcxa"                     
> gsub("[ab]","x",c("abcd","dcba"))   ## g表示全局
[1] "xxcd" "dcxx"

 

> sub("[a-c]","x",c("abcde","edcba"))   ## 将a-c中的任一个替换为x
[1] "xbcde" "edxba"
> gsub("[a-c]","x",c("abcde","edcba"))  ## g表示全局
[1] "xxxde" "edxxx"

 

> sub("[1-9]","x",c("ab001","001ab"))    ## 将1-9中的任一字符替换我x 
[1] "ab00x" "00xab"

 

> sub("a.*b","x",c("aabab","eabbe"))     ## 将a后1至任意多个字符到b替换为x
[1] "x"   "exe"

 

> sub("a.*b","x",c("aabab","eabbe"))     ## 没有？表示贪婪匹配
[1] "x"   "exe"
> sub("a.*?b","x",c("aabab","eabbe"))    ## 有？表示非贪婪匹配
[1] "xab"  "exbe"

 

来源：https://blog.csdn.net/ISMedal/article/details/79450820