如何在R中使用str_split（）？

Question

I want to split this string in several substrings:

BAA33520.2|/gene="vpf402",/product="Vpf402"|GI:8272373|AB012574|join{7347:7965, 0:591}

The separator is | (ascii 124).
It works with all other separators but not with this one.

Answer 1

?regex

Two regular expressions may be joined by the infix operator | ; the resulting regular expression matches any string matching either subexpression. For example, abba|cde matches either the string abba or the string cde . Note that alternation does not work inside character classes, where | has its literal meaning.

The fundamental building blocks are the regular expressions that match a single character. Most characters, including all letters and digits, are regular expressions that match themselves. Any metacharacter with special meaning may be quoted by preceding it with a backslash. The metacharacters in extended regular expressions are . \\ | ( ) [ { ^ $ * + ? . \\ | ( ) [ { ^ $ * + ? , but note that whether these have a special meaning depends on the context.

Thus:

stringr::str_split('BAA33520.2|/gene="vpf402",/product="Vpf402"|GI:8272373|AB012574|join{7347:7965, 0:591}', "\\|")

As @ Frank noted, you can do this in base::strsplit() by adding the fixed=TRUE :

strsplit('BAA33520.2|/gene="vpf402",/product="Vpf402"|GI:8272373|AB012574|join{‌​7347:7965, 0:591}',"|", fixed=TRUE)

However, you can also do this with stringr::str_split() by decorating the regular expression for the separator:

stringr::str_split('BAA33520.2|/gene="vpf402",/product="Vpf402"|GI:8272373|AB012574|join{7347:7965, 0:591}', 
                   regex("|", literal=TRUE))

Incidentally, stringr is pretty much just a slightly friendlier wrapper to stringi functions at this point and I highly recommend studying the stringi package as it contains some wonderful gems outside of string spiltting.