R: regex match in string vector

Labels: Informatics
Email ThisBlogThis!Share to XShare to Facebook

Finding Regex Matches in String Vectors

> grep("a+", c("abc", "def", "cba a", "aa"), value=FALSE) 
[1] 1 3 4 

> grep("a+", c("abc", "def", "cba a", "aa"), value=TRUE) 
[1] "abc" "cba a" "aa"

> regexpr("a+", c("abc", "def", "cba a", "aa"))
[1]  1 -1  3  1
attr(,"match.length")
[1]  1 -1  1  2 

> gregexpr("a+", c("abc", "def", "cba a", "aa"))
[[1]]  [1] 1    attr(,"match.length")  [1] 1
[[2]]  [1] -1   attr(,"match.length")  [1] -1
[[3]]  [1] 3 5  attr(,"match.length")  [1] 1 1
[[4]]  [1] 1    attr(,"match.length")  [1] 2

Replacing Regex Matches in String Vector

> sub("(a+)", "z\\1z", c("abc", "def", "cba a", "aa"))
[1] "zazbc"  "def"  "cbzaz a"   "zaaz" 

> gsub("(a+)", "z\\1z", c("abc", "def", "cba a", "aa"))
[1] "zazbc"  "def"  "cbzaz zaz" "zaaz"

Email ThisBlogThis!Share to XShare to Facebook

Labels: Informatics