是否可以使用ggplot在地图上叠加散点图?

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问题描述

我想画一张法国部门的地图(即法国的地区)，并在地图上标出点.我使用ggplot2绘制地图，但是当我想在地图上添加点时，R返回错误，提示它找不到组".

I would like to draw a map of French departements (ie districts in France) and plot points on the map. I use ggplot2 to draw the map but when I want to add points on the map, R returns an error which says that it cannot find 'group'.

library("ggplot2")
library("ggmap")

# load the contour of French departements
wg  <- read.csv("data/departements.csv")

metropoles  <- c("Paris", "Rennes", "Rouen", "Lille", "Marseille")
geo  <- geocode(metropoles)
met  <- data.frame(ville = metropoles, geo)

map  <- ggplot(data = wg, aes(x = long, y = lat, group = group)) +
geom_polygon() +
scale_x_continuous(limits = c(-7,10)) +
scale_y_continuous(limits = c(40,53)) +
coord_map() +
theme(axis.text = element_blank(), axis.title = element_blank())

map + geom_point(data = met, aes(x = lon, y = lat))

对于复制，您可以在此处和原始数据中找到原始数据R程序此处

For replication, you can find the raw data here and the R program here

推荐答案

@Roland的回答很好.问题是我已经将group定义为通用参数.

@Roland had the good answer. The problem is that I had defined group as a general argument.

ggplot() +
  geom_polygon(data = wg, aes(x = long, y = lat, group = group)) +
  scale_x_continuous(limits = c(-7,10)) +
  scale_y_continuous(limits = c(40,53)) +
  coord_map() +
  theme(axis.text = element_blank(), axis.title = element_blank())
  geom_point(data = met, aes(x = lon, y = lat))

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