Plotting yields over time by region
So far, you have used a function to plot yields over time for each crop, and you've added a census_region column to the crop datasets. Now you are ready to look at how the yields change over time in each region of the USA.
ggplot2 is loaded. corn and wheat have been fortified with census regions. plot_yield_vs_year() is available.
แบบฝึกหัดนี้เป็นส่วนหนึ่งของหลักสูตร
Introduction to Writing Functions in R
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# Plot yield vs. year for the corn dataset
___ +
# Facet, wrapped by census region
___(___(___))