grepl for a period “.” in R?

Question

Lets say I have a string \"Hello.\" I want to see if this string contains a period:

text <- \"Hello.\"
results <- grepl(\".\", text)

Answer 1

See the differences with these examples

 > grepl("\\.", "Hello.")
[1] TRUE
> grepl("\\.", "Hello")
[1] FALSE

the . means anything as pointed out by SimonO101, if you want to look for an explicit . then you have to skip it by using \\. which means look for a .

R documentation is extensive on regular expressions, you can also take a look at this link to understand the use of the dot.

Answer 2

I use Jilber's approach usually but here are two other ways:

> grepl("[.]", "Hello.")
[1] TRUE
> grepl("[.]", "Hello")
[1] FALSE

> grepl(".", "Hello.", fixed = TRUE)
[1] TRUE
> grepl(".", "Hello", fixed = TRUE)
[1] FALSE