如何修复美国地图中的叠加多边形？

Question

下面给出了重叠的多边形，如何修复？

library(ggplot2)
ggplot(data = map_data("state")) + geom_polygon(aes(long, lat, group = region), 
  color = "red", fill = "red", alpha = 0.2)

Answer 1

您应该使用group = group作为geom_poly的参数，请参见以下内容：

library(ggplot2)
ggplot(data = map_data("state")) + 
  geom_polygon(aes(long, lat, group = group), 
               color = "red", fill = "red", alpha = 0.2)

输出：