This should get you started; what the code does is:
- download US Census bureau shapefile via {tigris} package, in {sf} package format
- left joins your data to the shapefile, using county name as key
- plots a map via
ggplot2::geom_sf() call; all the usual ggplot formatting magic (legends, fill scales etc.) will apply
library(tidyverse)
library(tigris)
library(sf)
# shapefile of Alabama counties in {sf} format
alabama <- tigris::counties(state = 'AL', cb = T, class = 'sf')
# your data
data <- tribble(
~Date, ~County, ~State, ~Fips, ~Value,
'2020-06-21', 'Autauga', 'Alabama', 1001, 431,
'2020-06-21', 'Baldwin', 'Alabama', 1003, 420,
'2020-06-21', 'Barbour', 'Alabama', 1005, 272,
'2020-06-21', 'Bibb', 'Alabama', 1007, 126,
'2020-06-21', 'Blount', 'Alabama', 1009, 143,
'2020-06-21', 'Bullock', 'Alabama', 1011, 327,
)
# all Alabama counties, enriched for your data (where available)
chart_src <- alabama %>%
left_join(data, by = c("NAME" = "County"))
# a plot to start with
ggplot(chart_src) +
geom_sf(aes(fill = Value))