helingogo / regexcite

What the Package Does (One Line, Title Case)

NOTE: This is a toy package created for expository purposes, for the second edition of R Packages. It is not meant to actually be useful. If you want a package for factor handling, please see stringr, stringi, rex, and rematch2.

regexcite

The goal of regexcite is to make regular expressions more exciting! It provides convenience functions to make some common tasks with string manipulation and regular expressions a bit easier.

Installation

You can install the development version of regexcite from GitHub with:

# install.packages("devtools")
devtools::install_github("jennybc/regexcite")

Usage

A fairly common task when dealing with strings is the need to split a single string into many parts. This is what base::strplit() and stringr::str_split() do.

(x <- "alfa,bravo,charlie,delta")
#> [1] "alfa,bravo,charlie,delta"
strsplit(x, split = ",")
#> [[1]]
#> [1] "alfa"    "bravo"   "charlie" "delta"
stringr::str_split(x, pattern = ",")
#> [[1]]
#> [1] "alfa"    "bravo"   "charlie" "delta"

Notice how the return value is a list of length one, where the first element holds the character vector of parts. Often the shape of this output is inconvenient, i.e. we want the un-listed version.

That’s exactly what regexcite::str_split_one() does.

library(regexcite)

str_split_one(x, pattern = ",")
#> [1] "alfa"    "bravo"   "charlie" "delta"

Use str_split_one() when the input is known to be a single string. For safety, it will error if its input has length greater than one.

str_split_one() is built on stringr::str_split(), so you can use its n argument and stringr’s general interface for describing the pattern to be matched.

str_split_one(x, pattern = ",", n = 2)
#> [1] "alfa"                "bravo,charlie,delta"

y <- "192.168.0.1"
str_split_one(y, pattern = stringr::fixed("."))
#> [1] "192" "168" "0"   "1"