Summarizing by state
Another interesting column is land_area, which shows the land area in square miles. Here, you'll summarize both population and land area by state, with the purpose of finding the density (in people per square miles).
counties_selected <- counties %>%
select(state, county, population, land_area)
Это упражнение является частью курса
Data Manipulation with dplyr
Интерактивное практическое упражнение
Попробуйте выполнить это упражнение, дополнив этот пример кода.
counties_selected %>%
# Group by state
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# Find the total area and population
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