Something like A[grep('^ab', as.vector(A$M)),]
might work zhihua li wrote: > hi netters, > > i have a dataframe A with several columns(variables). the elements of > column M are character strings. so > A$M=c("ab","abc","bcd","ac","abcd","fg",....."fl"). > > i wanna extract all the rows where A$M match some regular expression > pattern. > for a simple example, let the pattern be just "ab", i wanna subset the > rows where A$M="ab" or "abc" or "abcd" or "abXX"......... > > i know i can write a loop,using some regular expression pattern > functions like grep row by row. but when A's size is pretty large, it's > inefficient. could anyone give me a hint about a faster code? > > thanks a lot!
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