在ggmap上覆盖形状文件

Question

我在ggmap地图上叠加形状文件时遇到问题。

当我单独运行时，形状文件很好，见下图。

library(ggmap)
library(grid)

la <- get_map(location="Los Angeles County", zoom=9)

# get base map layer
gg <- ggmap(la)

 library(broom)

  LaCountyTracts <- CalifCensusTracts %>% 
   tidy(region = "GEOID") %>%
   filter(grepl("06037", id))

 ggplot(LaCountyTracts, aes(long, lat, group = group) ) +
      geom_polygon(   fill = "grey40", 
           colour = "grey90", alpha = .7, size = .05) +
      coord_map() +
      theme_minimal() 

当组合ggmap和形状文件时，下面的代码会产生变形的形状图层。

 gg + geom_polygon(data=LaCountyTracts,aes(x=long, y=lat,group=group),
                      colour = "grey90", alpha = .7, size = .05)

Answer 1

从

更改了这一行

la <- get_map(location="Los Angeles County", zoom=9)

到

la <- get_map(location="Los Angeles County", zoom = 8)

并修复了问题