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  3. String Manipulation with stringr in R
  • 1

    String basics

    Free

    You'll start with some basics: how to enter strings in R, how to control how numbers are transformed to strings, and finally how to combine strings together to produce output that combines text and nicely formatted numbers.

  • 2

    Introduction to stringr

    Time to meet stringr! You'll start by learning about some stringr functions that are very similar to some base R functions, then how to detect specific patterns in strings, how to split strings apart and how to find and replace parts of strings.

  • 3

    Pattern matching with regular expressions

    In this chapter you'll learn about regular expressions, a language for describing patterns in strings. By combining regular expressions with the stringr functions you'll greatly increase your power to manipulate strings.

  • 4

    More advanced matching and manipulation

    Now for two advanced ways to use regular expressions along with stringr: selecting parts of a match (a.k.a capturing) and referring back to parts of a match (a.k.a back-referencing). You'll also learn to deal with and strings or patterns that contain Unicode characters (e.g. é).

  • 5

    Case studies

    Practice your string manipulation skills on a couple of case studies. You'll also learn a few new skills, reading strings into R and handling problems of case (e.g. A versus a).

Initializing

Exercise

What you see isn't always what you have

Take a look at line2, the string you just defined, by printing it:

line2

Even though you used single quotes so you didn't have to escape any double quotes, when R prints it, you'll see escaped double quotes (\")! R doesn't care how you defined the string, it only knows what the string represents, in this case, a string with double quotes inside.

When you ask R for line2 it is actually calling print(line2) and the print() method for strings displays strings as you might enter them. If you want to see the string it represents you'll need to use a different function: writeLines().

You can pass writeLines() a vector of strings and it will print them to the screen, each on a new line. This is a great way to check the string you entered really does represent the string you wanted.

Instructions

100 XP

We've put your lines from Alice's Adventures in Wonderland in a vector called lines.

  • Take a look at lines to see R's representation of the strings.
  • Pass lines to writeLines() to see the content of strings you've created.
  • By default writeLines() separates the strings with a newline, which you can change using the sep argument. Write lines to the screen again, but this time set the sep argument to a space, " ".
  • Finally, try using writeLines() on the string "hello\n\U1F30D". You'll learn about what's going on here in the next exercise.