I am trying to match string LLC from a list. The string could be any combination with upper and lower cases, such as llc,Llc,llC. How to construct a regular expression that include all possible upper/lower case combinations of the string? Many thanks!

CodePudding user response：

1. base

In the series of pattern matching functions in base (grep(), sub(), etc.), you could set the argument ignore.case to control case-sensitivity.

x <- c('Llc', 'lLc', 'llC')

grepl('LLC', x, ignore.case = TRUE)

# [1] TRUE TRUE TRUE

You could also insert (?i) to switch on case-insensitive mode. ((?-i) to switch off)

grepl('(?i)LLC', x)

# [1] TRUE TRUE TRUE

2. stringr

With stringr, you could control matching behaviour with modifier functions. (regex(), fixed(), etc.)

str_detect(x, regex('LLC', ignore_case = TRUE))

# [1] TRUE TRUE TRUE