Left joining a table to itself
So far, you've been inner joining a table to itself in order to find the children of themes like "Harry Potter"
or "The Lord of the Rings"
.
But some themes might not have any children at all, which means they won't be included in the inner join. As you've learned in this chapter, you can identify those with a left_join
and a filter()
.
This exercise is part of the course
Joining Data with dplyr
Exercise instructions
- Left join the themes table to its own children, with the suffixes
_parent
and_child
respectively. - Filter the result of the join to find themes that have no children.
Hands-on interactive exercise
Have a go at this exercise by completing this sample code.
themes %>%
# Left join the themes table to its own children
___ %>%
# Filter for themes that have no child themes
filter(___)