Search for pattern in datatable with grepl

I have a datatable, which looks like this:

test <- data.table(
        ID = 1:5,
        pattern = c("01234567 ~ 01234567 ~ 12345678 ~ 23456789 ~ A012345",
                    "A012345 ~ 12345678 ~ A01234 ~ 12345678 ~ 23456789 ~ A012345",
                    "A012345 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789",
                    "12345678 ~ 01234567 ~ 12345678 ~ 23456789",
                    "A0123456 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789")
        )

I want to know if the rows have a pattern, starting with a character (A-Z) and have less than 7 or more than 7 digits. For this, I want to add two new columns, named smaller7 and greater7, which say TRUE or FALSE.

I tried with this:

      # less than 7 digits
      test[, smaller7 := grepl("(^| )[A-Z].{1,5}($| )", test$pattern, ignore.case = TRUE)]
      
      # more than 7 digits
      test[, greater7 := grepl("(^| )[A-Z].{7,}($| )$", test$pattern, ignore.case = TRUE)]

The result is:

ID	pattern	smaller7	greater7
1	01234567 ~ 01234567 ~ 12345678 ~ 23456789 ~ A012345	FALSE	FALSE
2	A012345 ~ 12345678 ~ A01234 ~ 12345678 ~ 23456789 ~ A012345	TRUE	TRUE
3	A012345 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789	FALSE	TRUE
4	12345678 ~ 01234567 ~ 12345678 ~ 23456789	FALSE	FALSE
5	A0123456 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789	FALSE	TRUE

But the right output should be this:

ID	pattern	smaller7	greater7
1	01234567 ~ 01234567 ~ 12345678 ~ 23456789 ~ A012345	FALSE	FALSE
2	A012345 ~ 12345678 ~ A01234 ~ 12345678 ~ 23456789 ~ A012345	TRUE	FALSE
3	A012345 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789	FALSE	FALSE
4	12345678 ~ 01234567 ~ 12345678 ~ 23456789	FALSE	FALSE
5	A0123456 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789	FALSE	TRUE

Whats wrong with my grepl? I need a solution without splitting column. Thanks for your help!

Solution

I think you are just missing a few brackets here and there. I also tried to be a bit more explicit with the digits.

# less than 7 digits
test[, smaller7 := grepl("(^| )[[:alpha:]]+([[:alnum:]]{1,5})($| )", pattern),]
# more than 7 digits
test[, greater7 := grepl("(^| )[[:alpha:]]+([[:alnum:]]{7,})($| )", pattern),]
test
#   ID                                                     pattern smaller7 greater7
#1:  1         01234567 ~ 01234567 ~ 12345678 ~ 23456789 ~ A012345    FALSE    FALSE
#2:  2 A012345 ~ 12345678 ~ A01234 ~ 12345678 ~ 23456789 ~ A012345     TRUE    FALSE
#3:  3         A012345 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789    FALSE    FALSE
#4:  4                   12345678 ~ 01234567 ~ 12345678 ~ 23456789    FALSE    FALSE
#5:  5        A0123456 ~ 12345678 ~ 01234567 ~ 12345678 ~ 23456789    FALSE     TRUE

Also here is the alternative with [A-z] and [A-z0-9].

# less than 7 digits
test[, smaller7 := grepl("(^| )[A-z]+([A-z0-9]{1,5})($| )", pattern),]
# more than 7 digits
test[, greater7 := grepl("(^| )[A-z]+([A-z0-9]{7,})($| )", pattern),]

But from your description what you probably want is "(^| )[[:alpha:]]+([[:alnum:]]{1,6})($| )" instead of "(^| )[[:alpha:]]+([[:alnum:]]{1,5})($| )" to really get something under 7 and on the other hand {8,}. Otherwise you get also lengths which are exactly 7.