find furthest point from wca competitions in continental us

furthest.R

# mostly borrowed from https://stackoverflow.com/questions/38253715/r-find-point-farthest-from-set-of-points-on-rasterized-usa-map
library("sf")
library("rgdal")
library("raster")
library("RMySQL")

# competition data from sql
mysqlconnection = dbConnect(RMySQL::MySQL(),
                            dbname='wca_dev',
                            host='localhost',
                            port=3306,
                            user='root',
                            password='password')
# change query to use different date, etc
all_comps = dbGetQuery(mysqlconnection, "select id, latitude/1000000 as lat, longitude/1000000 as lon from competitions where start_date < 20230819")

# shp file
us_shp <- read_sf("/users/louismeunier/downloads/cb_2018_us_state_20m/cb_2018_us_state_20m.shp")

# only want cont. us
continental <- us_shp[!us_shp$NAME %in% c("Alaska", "Hawaii", "Puerto Rico"), ]

# rasterize
r <- raster(ncol=100, nrow=100)
extent(r) <- extent(continental)
rr <- rasterize(continental, r)

coords <- cbind(all_comps$lon, all_comps$lat)

D <- distanceFromPoints(object=rr, xy=coords)

# ignore points outside cont. us
D[which(is.na(rr[]))] <- NA

plot(D, xaxt='n', yaxt='n')
points(coords, pch=19, cex=0.25)
lines(continental)

# get max point
D.dataframe <- data.frame(rasterToPoints(D))
D.dataframe.sorted <- D.dataframe[order(D.dataframe$layer),]
maxpoint <- D.dataframe[D.dataframe$layer ==max(D.dataframe$layer),]
points(maxpoint$x, maxpoint$y, pch=19, cex=1, col='red')