Background

Many articles need to use maps to display some data. Professional drawing software such as ARCGIS is more expensive and takes a long time to learn. The advantage of drawing with R is that everyone can install R and R maps have no copyright issues and are easy to use. The main R packages used are ggplot2, sf, rnaturalearth, rnaturalearthdata, etc. When you need to modify the picture, you only need to modify the code, which eliminates the cumbersome modification of the picture.

To determine the origin of the sample, so samples from different countries are collected, and the location of the origin needs to be marked on the map.

R packages

library(rnaturalearth)
library(rnaturalearthdata)
library(ggspatial)
library(sf)
library(ggplot2)
library(gpclib)
library(maptools)
library(maps)
library(mapdata)
library(sp)
library(raster)
library(RColorBrewer)
library(rgeos)

Code and results

The sampling sits could be created by R:

setwd("C:/blog/Dataset")
##load dataset within Latitude and longitude

XY <- read.csv('XY.csv')
## Have a look at dataset

head(XY)

##   Code        X         Y   Code_X
## 1    A 109.5812  31.30150 116.5812
## 2    B 136.5353 -22.05232 143.5353
## 3    C -47.5500 -15.47000 -40.5500
## 4    D -75.4200  45.27000 -68.4200
## 5    E 116.2000  39.55000 123.2000
## 6    F -78.3500  -0.15000 -71.3500

##choose word map
world <- ne_countries(scale = "medium", returnclass = "sf")

##set theme
theme_set(theme_bw())
## plot
g1 <- ggplot(data = world)+
  geom_sf() +
  ##set points of positions
  geom_point(data=XY,aes(x=X,y=Y),pch=21,fill="yellow",col="grey40",size=5)+
  ##name points
  geom_text(data= XY,aes(x=Code_X, y=Y, label=Code),
       color = "darkblue", fontface = "bold",size=5, check_overlap = FALSE)+
  labs(title="The sampling sits created by R")+
  xlab("Longitude") + ylab("Latitude")+
  ##set font size
  theme(axis.text=element_text(size=12),
        axis.title=element_text(size=16))+
 ##Insert compass and scale
  annotation_scale(location = "bl", width_hint = 0.5) +
  annotation_north_arrow(
  location = "bl", which_north = "true", 
  pad_x = unit(0.75, "in"), pad_y = unit(0.5, "in"),
  style = north_arrow_fancy_orienteering)+
  theme(panel.grid.major = element_line(color = gray(.5), 
  linetype = "dashed", size = 0.5), 
  panel.background = element_rect(fill = "aliceblue"))

g1

## Scale on map varies by more than 10%, scale bar may be inaccurate

References

1. R-spatital,https://r-spatial.org/.