downloadPrecip.R - download precipitation data from NOAA Climate Prediction Center (does not require wget -- probably much easier to use wget instead)
calcSPI.R - calculate the Standardized Precipitation Index
plotSPI_simple.R - make a simple map of the SPI (good for sanity checks of calcSPI)
plotSPI_leaflet.R - create an interactive map of the SPI using Leaflet
spi_shiny_app/app.R - turn the Leaflet map into an interactive web app using Shiny. This web app is running here: https://chenerous.shinyapps.io/spi_shiny_app/
forecastYield.R - use SPI to predict corn yields in the US using a stepwise linear regression and a random forest method and compare the results:
