ggplot2로 지도 그리기

map

ggplot2

RColorBrewer

Author

Jong-Hoon Kim

Published

August 30, 2023

ggplot2를 이용하여 지도 그리기를 해보자. 지도는 shapefile에 담겨져 있다고 가정하자. shapefile을 읽는 방법은 여러가지가 있을 수 있는데 sf 패키지의 st_read 혹은 read_sf 함수를 이용한 후 ggplot2의 geom_sf를 이용하여 그리는 것이 가장 쉬운 것 같다.

library(sf)
kor <- st_read("gadm41_KOR_1.shp")

Reading layer `gadm41_KOR_1' from data source 
  `C:\Users\jonghoon.kim\Documents\myblog\blog\posts\drawing-map\gadm41_KOR_1.shp' 
  using driver `ESRI Shapefile'
Simple feature collection with 17 features and 11 fields
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: 124.6097 ymin: 33.11236 xmax: 131.8715 ymax: 38.61177
Geodetic CRS:  WGS 84

# kor <- read_sf(dsn="C:/Users/jonghoon.kim/Documents/myblog/posts/drawing-map", layer="gadm41_KOR_1")
set.seed(42)
# normalized number of characters of the name of the admin unit (level 1)
char_len <- sapply(kor$NAME_1, nchar)
kor$prop_char <- char_len / max(char_len)

library(ggplot2)
plt <- ggplot(kor)+
  geom_sf(aes(fill=prop_char))+
  scale_fill_viridis_c(name="Normalized\ncharacter length", limits=c(0,1)) +
  theme_minimal()+
  theme(legend.position="right")

plt

# use color brewer 
library(RColorBrewer)
pal <- brewer.pal(9,"YlOrBr")
plt <- plt + 
  scale_fill_gradientn(name="Normalized\ncharacter length", colors=pal, limits=c(0,1))
  
plt

# Clear some background stuff
plt <- plt +
  theme(panel.background = element_blank(), # bg of the panel
        plot.background = element_blank(), # bg of the plot
        legend.background = element_blank(), # get rid of legend bg
        legend.box.background = element_blank(),
        panel.spacing = unit(c(0,0,0,0), "null"),
        plot.margin = unit(c(0,0,0,0), "null"),
        axis.line = element_blank(),
        axis.text.x = element_blank(),
        axis.text.y = element_blank(),
        axis.ticks = element_blank(),
        axis.title.x = element_blank(),
        axis.title.y = element_blank(),
        panel.border = element_blank(),
        panel.grid.major = element_blank(),
        panel.grid.minor = element_blank(),
        legend.position = "bottom",
        plot.title = element_text(hjust=0.5, size=12))
plt