[英]How can I build regular expression in R?
I have the following dataframe: 我有以下数据框:
aa123 aa123.1 aa456 aa456.1
1 2 3 4
I want to take only the columns that match a pattern: "aa[numbers].1". 我只想选择与模式匹配的列:“ aa [数字] .1”。 In other words to extract only the columns that end with ".1".
换句话说,仅提取以“ .1”结尾的列。
I have tried to use regular expression pattern for grep and dplyr select/filter + ends_with() with pattern = ".1" 我尝试对grep和dplyr select / filter + ends_with()使用正则表达式模式,其模式=“ .1”
But nothing seems to work, please advise me how can I build such pattern and point me to a guide how in the future to build the pattern I need. 但是似乎没有任何效果,请告诉我如何构建这种模式,并为我提供指南,以指导将来如何构建所需的模式。
You want to use a regular expression that matches a dot ( \\.
) followed with 1
followed with end of string ( $
). 您想使用一个正则表达式,该表达式与一个点(
\\.
)匹配,后跟1
然后是字符串结尾( $
)。
Use the following regex then: 然后使用以下正则表达式:
"\\.1$"
The dot must be escaped to match a literal dot. 点必须转义以匹配文字点。
See the regex demo . 参见regex演示 。
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