在R中绘制省界线

Question

我想绘制我的报告的等值线图。我已经从GADM下载了数据。我成功绘制了等值线图，但是当我添加边界时，发生了错误。出现了很多蓝线。

我的代码是：

#Read Database 
HCM <- read.csv("HCM.csv") 

#Load Packages 
library(plyr) 
library(sp) 
library(ggplot2) 
library(rgeos) 
library(maptools) 
library(scales) 

#Read Map (Map downloaded from GADM) 
vie_map1 <- readRDS('VNM_adm1.rds') 
vie_map <- fortify(vie_map1, region = "ID_1") 

#Draw the map 
ggplot() + 
    geom_map(data = HCM, aes(map_id = ID, fill = WeightRange), 
      map = vie_map) + expand_limits(x = vie_map$long, y = vie_map$lat) 

但是，当我想补充的界限，一些错误的发生（蓝色直线）。添加边界的代码是：

# Add the boundaries 
ggplot() + 
    geom_map(data = HCM, aes(map_id = ID, fill = WeightRange), 
      map = vie_map) + expand_limits(x = vie_map$long, y = vie_map$lat)+ 
geom_path() + 
    geom_path(data = vie_map, aes(x = long, y = lat), color = "blue") + 
    theme_bw() 

请告诉我如何解决它（删除直线）。

Answer 1

同时设定group的geom_path美学映射中，不仅x和y：

library(ggplot2) 
library(raster) 
library(maptools) 
vie_map1 <- getData("GADM", country="VNM", level=1) 
# trying URL 'http://biogeo.ucdavis.edu/data/gadm2.8/rds/VNM_adm1.rds' 
# Content type '' length 2765340 bytes (2.6 MB) 
# downloaded 2.6 MB 
vie_map <- fortify(vie_map1, region = "ID_1") 
ggplot() + 
    geom_polygon(data = vie_map, aes(x = long, y = lat, group = group), fill = "grey90") + 
    geom_path(data = vie_map, aes(x = long, y = lat, group = group), color = "blue") + 
    theme_bw()