what does "\\3" mean in r

In R, the "\" is used to escape special characters in a regular expression. The number following the "\" indicates which character to use.

For example, "\t" represents a tab character and "\n" represents a newline character.

In the case of "\3", it represents the third group captured by a regular expression.

Here is an example of how it can be used:

main.r
# create a string
text <- "ABCD1234"

# extract the third group of digits using regular expression
gsub("([A-Z]+)([0-9]+)([0-9]{2})", "\\3", text)
# Output: "34"
162 chars
7 lines

In the above code snippet, we have used a regular expression to capture three groups:

• [A-Z]+: one or more uppercase letters
• [0-9]+: one or more digits
• [0-9]{2}: exactly two digits

We then use the gsub function with the second argument as "\3" to extract the third group.