Week 3: Discussion Section

Practice vector operations

Author

Alessandra Vidal Meza

Published

May 13, 2025

1. Learning Objectives

  • Explore topological relationships with sf functions: st_intersects(), st_intersection(), st_within(), etc.
  • Explore distance relationships with sf functions: st_distance(), st_within_distance(), and st_buffer()
  • Learn about spatial and distance-based joins
  • Practice writing error/warning messages and unit tests to diagnose outputs

2. Get Started

  • Create an .Rproj as your version controlled project for Week 3
  • Create a Quarto document inside your .Rproj
  • Download this data folder from Google Drive and move it inside your .Rproj
  • Load all necessary packages and read spatial objects
library(here)
library(tidyverse)
library(sf)
library(tmap)
sb_protected_areas <- read_sf(here::here("data", "cpad_super_units_sb.shp")) %>% 
  st_transform("ESRI:102009")

sb_city_boundaries <- read_sf(here::here("data", "sb_city_boundaries_2003.shp")) %>%
  st_transform("ESRI:102009")

sb_county_boundary <- read_sf(here::here("data", "sb_county_boundary_2020.shp")) %>%
  st_transform("ESRI:102009")

aves <- read_sf(here::here("data", "aves_observations_2020_2024.shp")) %>%
  st_transform("ESRI:102009")

3. Your Task

You will be wokring with the following datasets:

  • Santa Barbara County’s City Boundaries (Santa Barbara County)
  • California Protected Areas Database (CPAD)
  • iNaturalist Research-grade Observations, 2020-2024 (via rinat)

Now, to meet this week’s learning objectives, your task:

  1. Find how many bird observations are within protected areas in Santa Barbara County
  • Show the different outputs from a spatial subset and a spatial join
  • Bonus Challenge: Try it out with a 5 km buffer around the protected areas too!
  1. Find the protected areas within 15 km of a city in Santa Barbara County
  • Hint: Use dplyr::filter() to select a city from sb_city_boundaries
  • Explore the different outputs with st_intersects(), st_intersection(), and st_within()
  • Practice a distance-based join with st_is_within_distance()
  1. Find the distance between your city of choice and a protected area of your choice
  • Note: st_distance() finds the distance between the geometries’ edges