1. Point Data: Outline Functions

[mitchellmanware]

Section 1 of the 'Introduction to Spatial Analysis with Environmental Data' will focus on point data type.

Data use case: EPA PM_2.5 daily data for 2021

• https://aqs.epa.gov/aqsweb/airdata/download_files.htmlta

1.1 Point Data

• Setup
  • Packages used: sf and sftime (use of sftime still needs to be introduced)
  • Download data with utils::download.file()
  • Unzip data with utils::unzip()
  • Read point data with sf::st_read()
  • Data cleaning with base R (subset to parameters of interest, checking class, summarize data)
  • Check coordinate reference system with sf::st_crs
• Plot points
  • Plot points with base plot()
  • Introduce ggplot2 and ggpubr to make publication-quality figures
• Exploratory analyses
  • Calculate annual mean concentration for each monitor with dplyr
  • Subset to three highest air pollution monitors with dplyr
  • Plot time series of PM_2.5 measurements with ggplot
  • utilize + facet_wrap() functionality