在R中制作一个等值线:合并来自多个州的邮政编码shapefile

library(sf)
library(dplyr)
library(ggplot2)

# 读取shapefile
state_shapes <- c("state1.shp", "state2.shp", "state3.shp") %>%
  map(st_read) %>%
  bind_rows()

# 合并邮政编码数据
zipcode_data <- c("zipcode_state1.csv", "zipcode_state2.csv", "zipcode_state3.csv") %>%
  map(read.csv) %>%
  bind_rows()

# 将邮政编码数据与shapefile合并
merged_data <- zipcode_data %>%
  st_as_sf(coords = c("longitude", "latitude"), crs = 4326) %>%
  st_join(state_shapes)

# 制作等值线图
ggplot() +
  geom_sf(data = merged_data, aes(fill = zipcode)) +
  scale_fill_viridis_c(option = "plasma") +
  theme_void() +
  theme(legend.position = "bottom") +
  labs(title = "邮政编码等值线图", fill = "邮政编码")