Data Analysis with R, Second Edition - Second Edition

What are regular expressions?

Regular expressions (or regexes, as it is commonly abbreviated) is a formal grammar for describing patterns in text/strings. In general purpose programming languages, it is often used for things like verifying user input, but it is most often used in the context of statistical programming to transform the textual representation of raw data. Regular expressions are—at once—the plural form of a single regular expression, a powerful tool, an idea, and a language for describing patterns in text.

You might ask yourself: How do I work with this? You might first ask yourself: How does regex help me with data analysis? I compute on numbers, not strings!

Well, first, there are often strings/character vectors in datasets ...