R语言gsub替换字符工具的具体使用

时间:2021-05-20

gsub()可以用于字段的删减、增补、替换和切割,可以处理一个字段也可以处理由字段组成的向量。

具体的使用方法为:gsub("目标字符", "替换字符", 对象)

在gsub函数中,任何字段处理都由将“替换字符”替换到“目标字符”这一流程中实现,令替换字符为''''可实现删除,令替换字符为"目标字符+增补内容"可实现增补,替换和切割也是使用类似的操作。

> text <- "AbcdEfgh . Ijkl MNM"> gsub("Efg", "AAA", text) #将Efg改为AAA,区分大小写[1] "AbcdAAAh . Ijkl MNM"

任何符号,包括空格、Tab和换行都是可以识别的

> gsub(" I", "i", text) #可识别空格[1] "AbcdEfgh .ijkl MNM"

同时字符可以识别多个,进行批量置换

> gsub("M", "N", text) [1] "AbcdEfgh . Ijkl NNN"

除此之外,gsub还有其他批量操作的方法

> gsub("^.* ", "a", text) #开头直到最后一个空格结束替换成a[1] "aMNM"> gsub("^.* I(j).*$", "\\1", text) #只保留一个j[1] "j"> gsub(" .*$", "b", text) #第一个空格直达结尾替换成b[1] "AbcdEfghb"> gsub("\\.", "\\+", text) #句号.和加号+是特殊的,要添加\\来识别[1] "AbcdEfgh + Ijkl MNM"

Syntax Description \\d Digit, 0,1,2 ... 9 \\D Not Digit \\s Space \\S Not Space \\w Word \\W Not Word \\t Tab \\n New line ^ Beginning of the string $ End of the string \ Escape special characters, e.g. \\ is "\", \+ is "+" | Alternation match. e.g. /(e|d)n/ matches "en" and "dn" • Any character, except \n or line terminator [ab] a or b [^ab] Any character except a and b [0-9] All Digit [A-Z] All uppercase A to Z letters [a-z] All lowercase a to z letters [A-z] All Uppercase and lowercase a to z letters i+ i at least one time i* i zero or more times i? i zero or 1 time i{n} i occurs n times in sequence i{n1,n2} i occurs n1 - n2 times in sequence i{n1,n2}? non greedy match, see above example i{n,} i occures >= n times [:alnum:] Alphanumeric characters: [:alpha:] and [:digit:] [:alpha:] Alphabetic characters: [:lower:] and [:upper:] [:blank:] Blank characters: e.g. space, tab [:cntrl:] Control characters [:digit:] Digits: 0 1 2 3 4 5 6 7 8 9 [:graph:] Graphical characters: [:alnum:] and [:punct:] [:lower:] Lower-case letters in the current locale [:print:] Printable characters: [:alnum:], [:punct:] and space [:punct:] Punctuation character: ! " # $ % & ' ( ) * + , - . / : ; < = > ? @ [ \ ] ^ _ ` { | } ~ [:space:] Space characters: tab, newline, vertical tab, form feed, carriage return, space [:upper:] Upper-case letters in the current locale [:xdigit:] Hexadecimal digits: 0 1 2 3 4 5 6 7 8 9 A B C D E F a b c d e f

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