我希望使用经纬度点在R中绘制多个美国州的轮廓。现在我只能绘制每个州的轮廓,所以我想知道如何绘制多个美国州的轮廓(仅外线)。
library(tidyverse)
library(knitr)
library(broom)
library(stringr)
library(modelr)
library(forcats)
library(ggmap)
states <- map_data("state")# %>% as_tibble()
counties <- map_data("county")
il_df <- filter(fifty_states, id == "illinois")
midwest <- subset(fifty_states, id %in% c("illinois", "indiana", "iowa",
"kansas", "michigan", "minnesota",
"missouri", "nebraska", "north dakota",
"ohio", "south dakota", "wisconsin"))
il_mid <- ggplot(data = midwest, mapping = aes(x = long, y = lat, group = group)) +
coord_fixed(1.3) +
geom_polygon(color = "black", fill = "gray")
il_mid
我想知道如何在下面的图片中绘制粉色线条。
rgeos::gUnion
。 - r2evans