Chapter 6 Analysing spatial patterns

6.1 Learning outcomes

By the end of this practical you should be able to:

  1. Describe and evaluate methods for analysing spatial patterns
  2. Execute data cleaning and manipulation appropairte for analysis
  3. Determine the locations of spatial clusters using point pattern analysis methods
  4. Investigate the degree to which values at spatial points are similar (or different) to each other

6.2 Homework

Outside of our schedulded sessions you should be doing around 12 hours of extra study per week. Feel free to follow your own GIS interests, but good places to start include the following:

Assignment

From weeks 6-9, learn and practice analysis from the course and identify appropriate techniques (from wider research) that might be applicable/relevant to your data. Conduct an extensive methodological review – this could include analysis from within academic literature and/or government departments (or any reputable source).

Reading

This week:

Remember this is just a starting point, explore the reading list, practical and lecture for more ideas.

6.4 Introduction

In this practical you will learn how to begin to analyse patterns in spatial data. Using data you are already familiar with, in the first part of the practical, you will explore some techniques for analysing patterns of point data in R. Then, in the second part of the practial, you will explore spatial autocorrelation using R or ArcGIS…or both if you wish.

In this analysis we will analyse the patterns of Blue Plaques — you will see these placed on around the UK linking the buildings of the present to people of the past.

The question we want to answer is: “For any given London Borough, are the Blue Plaques within that borough distributed randomly or do they exhibit some kind of dispersed or clustered pattern?”

Before we progress, take a minute to go back and refelct on Grolemund and Wickham’s typical workflow of a data science (or GIS) project from workshop 1

To answer this question, we will make use of some of the Point Pattern Analysis functions found in the spatstat package.

#first library a few packages that we will use during the practical
#note you may need to install them first...
library(spatstat)
library(here)
library(sp)
library(rgeos)
library(maptools)
library(GISTools)
library(tmap)
library(sf)
library(geojson)
library(geojsonio)
library(tmaptools)

6.5 Setting up your data

Now, assuming that you’ve got a copy of your London Boroughs shapefile (from week 1) in your new week 6 folder, along with a shapefile of your Blue Plaques. If not.. read in the data from the ONS geoportal

##First, get the London Borough Boundaries
LondonBoroughs <- st_read(here::here("Prac1_data", "statistical-gis-boundaries-london", "ESRI", "London_Borough_Excluding_MHW.shp"))
## Reading layer `London_Borough_Excluding_MHW' from data source `C:\Users\Andy\OneDrive - University College London\Teaching\CASA0005\2020_2021\CASA0005repo\Prac1_data\statistical-gis-boundaries-london\ESRI\London_Borough_Excluding_MHW.shp' using driver `ESRI Shapefile'
## Simple feature collection with 33 features and 7 fields
## geometry type:  MULTIPOLYGON
## dimension:      XY
## bbox:           xmin: 503568.2 ymin: 155850.8 xmax: 561957.5 ymax: 200933.9
## projected CRS:  OSGB 1936 / British National Grid
# Or use this to read in directly.
#LondonBoroughs <- st_read("https://opendata.arcgis.com/datasets/8edafbe3276d4b56aec60991cbddda50_4.geojson")

Pull out London using the str_detect() function from the stringr package in combination with filter() from dplyr (again!). We will look for the bit of the district code that relates to London (E09) from the ‘lad15cd’ column data frame of our sf object.

library(stringr)
BoroughMap <- LondonBoroughs %>%
  dplyr::filter(str_detect(GSS_CODE, "^E09"))%>%
  st_transform(., 27700)

qtm(BoroughMap)