search for: abcpqrs

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2010 Jun 12
2
Logic with regexps
...two regular exdpressions ## rex1="abc", rex2="ijk", to return the elements of X which match ## rex1 AND do not match rex1: X <- c( "abcdefg", # Yes "abchijk", # No "mnopqrs", # No "ijkpqrs", # No "abcpqrs" ) # Yes rex1 <- "abc" rex2 <- "ijk" ix1<- grep(rex1,X) ix2<- grep(rex2,X) X[ix1[!(ix1 %in% ix2)]] ## [1] "abcdefg" "abcpqrs" Question: is there a way to construct 'rex' from 'rex1' and 'rex2' such that X[grep...