The objective of this script is to:
- Count the number of days each census tract of VA exceeded a 15 µg/m3 24-hour mean (WHO guideline) for 2.5 micron particulate matter (PM2.5)
- Graphically represent the exceedence days on a map of Virginia using the leaflet package
Maps for PM2.5 data can be viewed here (https://rpubs.com/morinajc/VAaq)