如何在地图上用ggmap绘制R中的地图上的箭头

Question

我正在试图在R中绘制各地点的地理坐标图，然后在它们之间的箭头指示特定的航班路线。

据对堆栈溢出这里一些早期的问题，这应该是可能使用ggmap和geom_segment，但它采用的方法，我在我下面的代码看起来像它不会工作：

library(htmlwidgets) 
library(leaflet) 
library(ggmap) 


#=============================== Data ===============================# 


#Retrieving coordinates for two airports 
Adress = c("Lufthavnsboulevarden 6, 2770 Kastrup, Denmark", "Edvard Munchs veg, 2061 Gardermoen, Norway") 

# This function geocodes a location (find latitude and longitude) using the Google Maps API 
geo <- geocode(location = Adress, output="latlon", source="google") 

#moving the data around, so that second observation will be end-destination 
geo$lonend[1] <- geo$lon[2] 
geo$latend[1] <- geo$lat[2] 

#removing second row 
row_to_keep = c(TRUE, FALSE) 
geo = geo[row_to_keep,] 

#putting a number in there to make some dots for the airports 
geo$Number = 999 

#=============================== Ploting =============================# 

# get a Google map 
require(ggmap) 
map<-get_map(location='Europe', zoom=5, maptype = "terrain", 
      source='google',color='color') 

# plot it with ggplot2 
require("ggplot2") 
require("RColorBrewer") 
ggmap(map) + 
    geom_point(
    aes(x=lon, 
     y=lat, 
     show_guide = TRUE, 
     colour=Number), 
    data=geo, 
    alpha=.8, 
    na.rm = T) + 
    scale_color_gradient(low="beige", high="blue") 

#Set the pointer from (y,x) => (yend,xend) using geom-segment 
ggmap(map, extent = "device", ylab = "lat", xlab = "lon") + 
    geom_segment(aes(y = geo$lon, x = geo$lat, yend = geo$lonend, xend = geo$latend)) 

你有对于我做错了什么的建议？

Answer 1

您的细分未被绘制，因为您将经度和纬度混淆，x对应于经度，y对应于纬度。此外，你应该使用data = geo和aes()

ggmap(map, extent = "device", ylab = "lat", xlab = "lon") + 
    geom_segment(data = geo, aes(y = lat, x = lon, yend = latend, xend = lonend)) 

同时删除geo$，为了显示一个箭头只是增加arrow = arrow()到geom_segment：

ggmap(map, extent = "device", ylab = "lat", xlab = "lon") + 
    geom_segment(data = geo, aes(y = lat, x = lon, yend = latend, xend = lonend), 
       arrow = arrow())