Search and replace

The function str_replace() is a general function to replace parts of a string. A common application is to replace something with an empty string - which is a simple way to remove unneeded parts from a string.

With capturing groups, str_replace() gets even more interesting: They enable you to change the order of things. By adding so called "backreferences" to the replacement, str_replace() will replace these references with the contents of the corresponding capturing group. For example: If you write \\1, this will be replaced with the 1st capturing group.

In this exercise, you'll see the first use (remove a substring) and the second (reorder two parts of a string) side by side. In the scope, you'll find the variable top_10_lines from the last exercise.

Deze oefening maakt deel uit van de cursus

Intermediate Regular Expressions in R

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Oefeninstructies

Remove 3D from the end of each line in top_10_lines by replacing it with an empty string.
Form a new sentence with the two capturing groups. Reorder them so they result in e.g. "Karate Kid is on rank 1".

Praktische interactieve oefening

Probeer deze oefening eens door deze voorbeeldcode in te vullen.

# Remove a space followed by "3D" at the end of the line
str_replace(
  top_10_lines,
  pattern = "___",
  replacement = ___
)

# Use backreferences 2 and 1 to create a new sentence
str_replace(
  top_10_lines,
  pattern = "(\\d+)\\. (.*)",
  replacement = "___ is at rank ___"
)

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