if (FALSE) {
library(maps)
data(world.cities)
cities_lon_lat <- world.cities[!duplicated(world.cities$name),]
rownames(cities_lon_lat) = cities_lon_lat[,1]
cities_lon_lat <- cities_lon_lat[cities_lon_lat$pop > 50000,]
cities_lon_lat <- cities_lon_lat[,4:5]
}
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