CODEWITHSUNDEEP
rggplot2geospatial
Mark R
Mark R

Reputation: 1021

Remove unwanted graticule lines on globe with geom_sf()

The following code creates graticule lines for the opposite side of the earth. How can I suppress just those lines, but not all graticules?

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

world.sf <- World # from tmap
world.sf %>% 
  filter(continent == "Africa") %>% 
  st_transform("+proj=chamb +lat_1=22 +lon_1=0 +lat_2=22 +lon_2=45 
               +lat_3=-22 +lon_3=22.5 +datum=WGS84 +type=crs") %>% 
  ggplot() + 
  geom_sf(aes(fill = economy))

Upvotes: 1

Views: 57

Answers (1)

Tim G
Tim G

Reputation: 4157

Inspired by this great answer and this we can first remove the graticule lines and then add custom lines back. I referred to this picture

out1 Source

Res

res

compared to before

before

library(tmap)
library(sf)
library(tidyverse)
data("World")

crs <- "+proj=chamb +lat_1=22 +lon_1=0 +lat_2=22 +lon_2=45 +lat_3=-22 +lon_3=22.5 +datum=WGS84 +type=crs"
len <- 200
lat_seq <- seq(40, # latitude from __
               -40,  # latitude until
               len = len)
lon_seq <- seq(-20, # longitude from |
               60, # longitude until
               len = len)

latlon <- st_multilinestring(
  c(lapply(seq(-20, 
               60, 
               20), # adjust step size 
           \(lon) cbind(rep(lon, len), lat_seq)),
    lapply(seq(40, 
               -40, 
               -20), # adjust step size 
           \(lat) cbind(lon_seq, rep(lat, len))))
) |> 
  st_sfc(crs = "WGS84") |> 
  st_sf() |> 
  st_transform(crs)

# Plot
World %>% 
  filter(continent == "Africa") %>% 
  st_transform(crs) %>% 
  ggplot() +
  theme(panel.grid.major = element_blank()) +
  geom_sf(data = latlon, 
          linewidth = 0.3, # adjust as needed
          color = "white") +
  geom_sf(aes(fill = economy))

Upvotes: 1

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