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I am using data table and I want to mark out observations with a substring ".." in a longer string. After looking at How to select R data.table rows based on substring match (a la SQL like) I tried

like("Hi!..", "..")

which returns TRUE and

like("Hi!..", "Bye")

returns FALSE. However, surprisingly,

like("Hi!". "..")

returns TRUE! If this is a feature, why is that? And what can I use instead if I want to check a substring for non-letter characters?

Mullvadsungen
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2 Answers2

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You have to escape the special character "." with "\":

like("Hi!", "\\.\\.")

ha-pu
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The second argument to like() is a regular expression and . has a special meaning in regex; it matches all characters. If you want to look for . literary, then add the argument fixed = TRUE.

like("Hi!", "..", fixed = TRUE)
# [1] FALSE
like("Hi!..", "..", fixed = TRUE)
# [1] TRUE
sindri_baldur
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