在这个方法中,我们使用regex,使用一个外部模块,比如stringr。例子1:使用点选择字符这里我们将使用点(.)来选择字符串中的字符。string <- c("WelcometoGeeksforgeeks!") str_extract_all(string, "G..k") R Copy输出Geek R CopyExample 2: 使用 \D 选择字符串\D是用来选择regex中的
…: Other less frequently used arguments passed onto stri_opts_collator, stri_opts_regex, or stri_opts_brkiter multiline: If TRUE, $ and ^ match the beginning and end of each line. If FALSE, the default, only match the start and end of the input. comments: If TRUE, whitespace and c...
•x: string or string vector •ignore.case: if FALSE, the pattern matching is case sensitive and if TRUE, case is ignored during matching •perl: logical. Should perl-compatible regexps be used? Has priority over extended •fixed: logical. If TRUE, pattern is a string to be matched...
\\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...
library(stringr) Raising the Anchor, the^Anchor To set sail, we must raise the anchor at the beginning of the trip. When working with text data, you may need to match a regex pattern, but only if it appears as the first thing in the string. To do that, we use the^anchor. ...
Match any character except for - by default - newline, comparestri_opts_regex. ^ Match at the beginning of a line. $ Match at the end of a line. \ [outside of sets] Quotes the following character. Characters that must be quoted to be treated as literals are*?+[(){}^$|\.. ...
The symbols \< and \> match the empty string at the beginning and end of a word. The symbol \b matches the empty string at either edge of a word, and \B matches the empty string provided it is not at an edge of a word. (The interpretation of ‘word’ depends on the locale and...
Run Code Online (Sandbox Code Playgroud) 演示 正则表达式可以分解如下。(或者,将光标悬停在链接处表达式的每个部分上以获得其功能的说明。) (?: |^)# match a space or the beginning of the string(\d+)# match one or more digits and save to capture group 1(?<!# begin a negative lookbehind(...
…: Other less frequently used arguments passed onto stri_opts_collator, stri_opts_regex, or stri_opts_brkiter multiline: If TRUE, $ and ^ match the beginning and end of each line. If FALSE, the default, only match the start and end of the input. ...
grep的核心就是正则表达式(Regular Expressions,通常缩写为regex),所谓正则表达式,就是用某种模式去匹配一类字符串的一个公式,很多文本编辑器或者程序语言都支持该方式进行字符串的操作,最开始是由上文介绍的Unix工具grep之类普及的,后来得到广泛应用。尤其是Perl语言中将正则表达式发挥到了极致。