如何使用ggplot2在地图上添加经纬线?

您可以使用 coord_map ggplot参数 documented here

这将使用投影来改变坐标网格。曲线将包括等距投影,但您应该看起来 here 查看所有允许投影的列表。你选择哪一种是一种偏好。

使用 azequidistant (我认为这是 Azimuthal equidistant projection ),并手动添加标签:

axis_labels <- rbind(
                  data.frame(long = rep(-140,5),lat = seq(40,80,10), labels = seq(40,80,10)), # x axis labels
                  data.frame(long = seq(-140,-60,40),lat = rep(85,3), labels = seq(140,60,-40))  # y axis labels
)

   ggplot() +
  geom_polygon(data=countries,aes(x=long,y=lat,group=group),fill='white',color = "black") + 
  coord_map("azequidistant") +
  scale_x_continuous(breaks = seq(-140,60, by = 20))+
  scale_y_continuous(breaks = seq(40,80, by = 10)) +
  geom_text(data = axis_labels, aes(x = long, y = lat, label = labels)) +
  theme_bw() +
  theme(panel.grid.major = element_line(colour = "grey"),
        panel.border = element_blank(),
        axis.text = element_blank())

您可以使用一个单独的空间数据网格层,然后根据加拿大图层投影该网格层。

您可以在以下网址找到免费的网格层下载: NaturalEarthData .

countries<-readOGR("Canada.shp", layer="Canada")
grat <- readOGR("graticule.shp", layer="graticule")

grat_prj <- spTransform(grat, CRS(countries))

ggplot() + 
geom_polygon(data=countries, aes(x=long,y=lat,group=group),fill='white',color = "black") + 
geom_path(data=grat_prj, aes(long, lat, group=group, fill=NULL), linetype="solid", color="grey50")