library(stringr) x <- c('ondaX', 'ondasX', 'ondasssX', 'onda', 'ondas') str_extract(x, regex('ondas??X')) str_extract(x, regex('ondas*?X'))
Standard input is empty
[1] "ondaX" "ondasX" NA NA NA [1] "ondaX" "ondasX" "ondasssX" NA NA
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