Week 2: Discussion Section

Reference

Refer to the Plotting Geospatial Data resource to help get you started.

Learning Objectives

• Use sf::st_read() to read multiple vector data types
• Retreive the CRS of a vector object with sf::st_crs()
• Transform CRS and match across all vector data types with sf::st_transform()
• Perform dplyr attribute manipulations (e.g. filter(), mutate(), select())

Data

• Colombia’s Terrestrial Ecosystems (The Nature Conservancy/NatureServe)
• Colombia’s Roads (Esri)
• Bird Observations (DATAVES)

Get Started

Let’s load the necessary packages:

library(here)
library(tidyverse)
library(sf)
library(tmap)

Now, to meet our learning objectives, your task:

1. Read in the data for Colombia’s ecoregions, roads, and bird observations

• Use st_read() to read vector data (e.g., .shp, .gdb)
• Use rename() or mutate() to rename the columns decimal_longitude and decimal_latitude to long and lat in aves and sf::st_as_sf() to convert it into an sf object
  • Hint: To convert a table into a vector object, you can use st_as_sf() but remember to check the class() of an object first!

2. Check class() of all vector objects (including the converted aves) and use sf::st_geometry_type() to check the geometry type
3. Use filter() to select a macro region of interest from N1_MacroBi in Colombia’s ecoregions dataset and save as a new vector data

• Check class() of the new vector data
• Plot the new vector data using tmap

4. Use st_crs() to retrieve CRS of all vector objects and assign a new CRS

• Bonus: Check units of your object with st_crs()$units
• Check CRS of all vector objects with st_crs()
• st_crs() <- NA is a brute force way to remove a CRS, instead:
  • For the bird observations dataset, extract the longitude and latitude from the geometry column and use sf::st_drop_geometry()
  • Convert long and lat into a geometry again with st_as_sf() to obtain a proper sf data frame

5. Let’s bring all vector data types together

• Check that the CRS of the ecoregions and roads datasets match
• Transform CRS of the bird observations data using sf::st_transform() to match with the other datasets
• Use tmap to plot the ecoregions, roads, and bird observations together