CRAN Recipes: DPLYR, Stringr, Lubridate, and RegEx in R

© The Author(s), under exclusive license to APress Media, LLC, part of Springer Nature 2021

W. YarberryCRAN Recipeshttps://doi.org/10.1007/978-1-4842-6876-6_5

5. Typical Uses

William Yarberry¹  

(1)

Kingwood, TX, USA

 

5.1 Test for a Match¹

The simplest patterns match exact strings:

x <- c("apple", "banana", "pear")

str_extract(x, "an")

## [1] NA   "an" NA

This syntax is case sensitive:

bananas <- c("banana", "Banana", "BANANA")

str_detect(bananas, "banana")

## [1]  TRUE FALSE FALSE

str_detect(bananas, regex("banana", ignore_case = TRUE))

## [1] TRUE TRUE TRUE

The next step up in complexity is ., which matches any character except a newline:

str_extract(x, ".a.")

## [1] NA    "ban" "ear"

You can allow . to match everything, including \n, by setting dotall = TRUE: ...