“'\w' is an unrecognized escape” in grep

问题

I'm using grep in some projects in R (which uses a perl=TRUE flag) and for the life of me I can't figure out why R keeps throwing errors. My query is as follows:

d$SomeColumn[grep("(?ix)<VNW[^;]*;(dis|dat)> \w*<N\(", d$Right, perl=TRUE)] <- 1

However, R throws the following error:

Error: '\w' is an unrecognized escape in character string starting ""<VNW[^;]*;(dis|dat)> \w"

回答1:

You need to escape the backslashes one more time in r.

d$SomeColumn[grep("(?ix)<VNW[^;]*;(dis|dat)> \\w*<N\\(", d$Right, perl=TRUE)] <- 1

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来源：https://stackoverflow.com/questions/27528581/w-is-an-unrecognized-escape-in-grep