library(maps)
usamap <- map_data("state")
seal.sub <- subset(seals, long > -130 & lat < 45 & lat > 40)
ggplot(seal.sub, aes(x = long, y = lat)) +
annotation_map(usamap, fill = "NA", colour = "grey50") +
geom_segment(aes(xend = long + delta_long, yend = lat + delta_lat))
seal2 <- transform(seal.sub,
latr = cut(lat, 2),
longr = cut(long, 2))
ggplot(seal2, aes(x = long, y = lat)) +
annotation_map(usamap, fill = "NA", colour = "grey50") +
geom_segment(aes(xend = long + delta_long, yend = lat + delta_lat)) +
facet_grid(latr ~ longr, scales = "free", space = "free")
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