In-class Exercise 3

3.1 Overview

3.2 Installing the Required Packages

Since maptools is retired and binary is removed from CRAN, we will be downloading it from the posit public package manager snapshots.

Note: It is important to add eval:false in the code chunk as shown below after installation is complete to avoid it being executed every time the quarto document is being rendered.

install.packages("maptools",repos = "https://packagemanager.posit.co/cran/2023-10-13")

pacman::p_load(sf,tmap,tidyverse)

3.3 The Data

mpsz_sf <- st_read(dsn="data/MasterPlan2014SubzoneBoundaryWebSHP/", 
                   layer="MP14_SUBZONE_WEB_PL")

Reading layer `MP14_SUBZONE_WEB_PL' from data source 
  `/Users/georgiaxng/georgiaxng/is415-handson/In-class_Ex/In-class_Ex03/data/MasterPlan2014SubzoneBoundaryWebSHP' 
  using driver `ESRI Shapefile'
Simple feature collection with 323 features and 15 fields
Geometry type: MULTIPOLYGON
Dimension:     XY
Bounding box:  xmin: 2667.538 ymin: 15748.72 xmax: 56396.44 ymax: 50256.33
Projected CRS: SVY21

The code chunk below, st_union() is used to derive the coastal outline sf tibble data.frame.

sg_sf <-mpsz_sf %>%
  st_union()

plot(sg_sf)

3.4 Viewing

The below chunk of code imports the ACLED Myanmar data, converts it into a spatial format, changes the coordinate system, and formats the event dates into a standard date format.

acled_sf <- read_csv("data/ACLED_Myanmar.csv") %>% 
  st_as_sf(coords = c(
    "longitude", "latitude"), crs = 4326) %>% 
  st_transform(crs= 32647)%>%
  mutate(event_date = dmy(event_date))

This code produces an interactive map displaying dots for events in 2023 or classified as “Political violence.

tmap_mode('view')
acled_sf %>%
  filter(year == 2023 |
           event_type == "Political violence") %>%
  tm_shape()+
  tm_dots()
tmap_mode('plot')