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Exercise

Using summarize, top_n, and count together

In this chapter, you've learned to use five dplyr verbs related to aggregation: count(), group_by(), summarize(), ungroup(), and top_n(). In this exercise, you'll use all of them to answer a question: In how many states do more people live in metro areas than non-metro areas?

Recall that the metro column has one of the two values "Metro" (for high-density city areas) or "Nonmetro" (for suburban and country areas).

counties_selected <- counties %>%
  select(state, metro, population)
Instructions 1/3
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  • 1

    For each combination of state and metro, find the total population as total_pop.

  • 2

    Extract the most populated row from each state, which will be either Metro or Nonmetro.

  • 3

    Ungroup, then count how often Metro or Nonmetro appears to see how many states have more people living in those areas.

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