Regular expressions
The commands examined in the previous section lack flexibility, but they are straightforward in their implementation. The use of regular expressions, on the other hand, offers a more elegant approach in many circumstances, but they can be more complex. We briefly examine a few commands that allow string manipulations via regular expressions, and we assume that you are familiar with regular expressions. To get more information about regular expressions in R you can use the help(regular expression) command.
In this section, we will focus on the gregexpr and gsub commands. There are a number of other commands that are listed when you enter the help(gregexpr) command. Also, the commands have a number of options, but we will only examine their most basic forms. As a quick note, the pattern submitted to the grep command discussed earlier can also be a regular expression.
The gregexpr command is a general command that returns the number of results with respect to the regular...
