Plotting State Border without Water using R and Raster?

Question

Suppose I want to plot New York or Ohio using R:

library('ggplot2')
library('map')
library('raster')

map <- raster::getData("GADM",country='USA',level=1)
map <- map[map$NAME_1 %in% c('Ohio'),]
map <- map_data(map)

ggplot() + 
  theme_void() +
  geom_polygon(data = map, 
           aes(x=long, y = lat, group = group), 
           fill="grey", alpha=0.3)

Here are the results:

How can I not display extra land in the Ohio plot, and only display land for New York?

It looks like it plots the state borders, see google maps for comparison.

Answer 1

Similarly to what you are getting for New York, the extra bit in Ohio represents the state border on Lake Erie and might therefore be a property of the GADM data. This approach uses the data from the maps package and plots the state borders on land:

library('ggplot2')
library('maps')

map <- map_data('state')
ohio <- subset(map, region %in% "ohio")
newyork <- subset(map, region %in% "new york")

ggplot() + 
  theme_void() +
  geom_polygon(data = ohio, 
               aes(x=long, y = lat, group = group), 
               fill="grey", alpha=0.3)
ggplot() + 
  theme_void() +
  geom_polygon(data = newyork, 
               aes(x=long, y = lat, group = group), 
               fill="grey", alpha=0.3)