160 R Programming for Bioinformatics
as email addresses and genomic sequences, as well as a variety of search and
optionally replace problems such as finding words or sentences with specific
b eginnings or endings. A regular expression is a pattern that describes a set
of character strings.
In R, there are three different types of regular expressions that you can use:
extended regular expressions, basic regular expressions and Perl-like regular
expressions. The first two types of regular expressions are implemented using
glibc, while the third is implemented using the Perl-compatible regular ex-
pressions (PCRE) library. We will present a view of the capabilities in R that
is based on the description in the manual page for regular expressions which
you