"why is not correct using &?"
Who says that it is not "correct" ? What you show is not a code error (underlined in red), it is a recommendation (underlined in orange)
Benefits:
- For scalar values && is (in general) faster than & because it only evaluates the right argument if the left argument is TRUE.
- Defensive programming: by using && you assert that its arguments are scalar. If later they are erroneously not scalar then && will stop with an error (rarher than continuing in some unknown state).
- Clarity to the reader
If you want to ignore this recommendation then right-click and select one of the "ignore" options.
