stringr-----str_extract
主页:https://cran.r-project.org/web/packages/stringr/index.html
#安装stringr包> install.packages('stringr')> library(stringr)
#stringr函数分类:
字符串拼接函数
字符串计算函数
字符串匹配函数
字符串变换函数
参数控制函数
#stringr字符串匹配函数
str_extract(string, pattern) str_extract_all(string, pattern, simplify = FALSE)
string: 字符串,字符串向量。 pattern: 匹配字符。
simplify: 返回值,TRUE返回matrix,FALSE返回字符串向量
从字符串中提取匹配模式
> val <- c("abca4", 123, "cba2") # 返回匹配的数字 > str_extract(val, "\\d") [1] "4" "1" "2" # 返回匹配的字符 > str_extract(val, "[a-z]+") [1] "abca" NA "cba" > val <- c("abca4", 123, "cba2") > str_extract_all(val, "\\d") [[1]] [1] "4" [[2]] [1] "1" "2" "3" [[3]] [1] "2" > str_extract_all(val, "[a-z]+") [[1]] [1] "abca" [[2]] character(0) [[3]] [1] "cba"
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