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.

Diese Übung ist Teil des Kurses

Intermediate Regular Expressions in R

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Anleitung zur Übung

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".

Interaktive Übung

Versuche dich an dieser Übung, indem du diesen Beispielcode vervollständigst.

# 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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