CODEWITHSUNDEEP
rregex
aprilian
aprilian

Reputation: 650

grep with $ in string

In R How do I grep something which has a $ in string. In This below example I need to grep string "NB6106$MU-MU.rma"

x<-c("NB6106$MU-MU.rma", "NB610634$MU-MU.rma")

x[grep(pattern="*6106$*.rma", x = x)] #does not work

Upvotes: 2

Views: 198

Answers (2)

iod
iod

Reputation: 7592

You need to escape it. $ by itself in a regular expression indicates the end of the string, so you need to tell R that here you mean it literally as a $, which is done by escaping. The escape character is \. So, in theory, you'll type in \$. BUT, since you're writing the pattern as a literal string (within quotes), you ALSO need to escape the escape character, so that R knows to transfer it literally to the regex interpretor. Hence: \\$.

Other issues with your code: * doesn't mean "any characters". It means "repeat the previous character zero or more times". . means any character, and .* means any number of any character, which is what you're looking for. And of course, if you want a literal period, you need to escape that too: \\.

Upvotes: 0

Wiktor Stribiżew
Wiktor Stribiżew

Reputation: 626960

You may use

x<-c("NB6106$MU-MU.rma", "NB610634$MU-MU.rma")
x[grep(pattern="6106\\$.*\\.rma", x = x)]

See the R demo

Details

  • 6106\\$ - 6106$ substring
  • .* - any 0+ chars
  • \\.rma - a .rma substring

If you plan to make sure you do not grep 11116106$...rma, you may use

"(^|\\D)6106\\$.*\\.rma$"

where (^|\\D) matches start of string (^) or (|) a non-digit char (\D), and $ at the end ensure the end of string appears right after .rma.

Upvotes: 6

Related Questions