emissions data analysis using graphical approach

Fine particulate matter (PM2.5) is an ambient air pollutant for which
there is strong evidence that it is harmful to human health. In the
United States, the Environmental Protection Agency (EPA) is tasked with
setting national ambient air quality standards for fine PM and for
tracking the emissions of this pollutant into the atmosphere.
Approximatly every 3 years, the EPA releases its database on emissions
of PM2.5. This database is known as the National Emissions Inventory
(NEI). You can read
For each year and for each type of PM source, the NEI records how many
tons of PM2.5 were emitted from that source over the course of the
entire year. The data that you will use for this assignment are for
1999, 2002, 2005, and 2008.