填充地图

 shi %>% 

  left_join(shi_df,by=c('市代码'='市代码')) %>% 

  filter(str_detect(市代码,'^62')) %>% 

  ggplot()+

  geom_sf(aes(fill=bl),size=0.01)+

  scale_fill_gradientn(breaks = c(15,30,45),

                       colors=c("gray", "yellow", "orange", "red"))