• This is going to be a very short introduction talk
• you have a lot of ground to cover in the worksheet
  • Spatial data formats in R (sp and sf)
  • Reading and writing spatial data in and out of R
  • Mapping with tmap
  • Cluster analysis (hotspots and coldspots)
  • Saving maps as PDFs, PNGs, TIFFs etc

• you have already made developed some visualisations of data attributes held in spatial data
  • the tb object in Session 3

df <- as.tibble(data.frame(georgia))
tb <- as.tibble(df)

• the georgia data is a SpatialPolygonsDataFrame

class(georgia)

## [1] "SpatialPolygonsDataFrame"
## attr(,"package")
## [1] "sp"

• In this session you will explore two spatial data formats
  • the old: sp
  • the new: sf
• they both hold the geometry of the geographic features and the attribute values
  • a bit like shapefiles
• however the plan is for sf to supersede sp
• hence the sf revolution
• we work mainly with sf but you will see that for some analyses we still have to work with sp at the moment.

• for both sf and sp
• to read / write georgia.shp with sf

setwd("/Users/geoaco")
g2 <- st_read("georgia.shp")
st_write(g2, "georgia.shp", delete_layer = T)

• to read / write georgia.shp with sp

new.georgia <- readOGR("georgia.shp") 
writeOGR(obj=new.georgia, dsn=".", layer="georgia", 
         driver="ESRI Shapefile") 

• maps built up as a series of layers
• exercise control
• like with ggplot

tm_shape(georgia_sf) +
  tm_fill("indianred") +
  tm_borders(lty = "dashed", col = "khaki") +
  tm_style_natural(bg.color = "grey75") +
  tm_shape(g) +
  tm_borders(lwd = 3) +
  tm_layout(title = "The State of Georgia", 
    title.size = 1, title.position = c(0.55, "top"))

• maps built up as a series of layers
• exercise control
• like with ggplot

• you will also construct some choropleth maps of variables
• for polygons / areas

• you will also construct some choropleth maps of variables
• for points

• you will calculate and map some local statistics
• cluster analysis with Moran’s I and G-statistic
• hotspot / coldspot

The key thing is sequence of operations

1. open a file There are a number of functions that do this:

pdf()
png()
tiff()

1. make the map
2. close the file

pdf(file = "MyPlot.pdf", other setting)
<tmap code?
dev.off()  

Example

setwd('~/Desktop/my_docs_mac/leeds_work/research/Groningen/')
# open the file
png(filename = "Figure1.png", w = 5, h = 7, units = "in", res = 150)
# make the map
tm_shape(georgia_sf) +
  tm_fill("olivedrab4") +
  tm_borders("grey", lwd = 1) +
  # the points layer
  tm_shape(pts_sf) +
  tm_bubbles("PctBlack", title.size = "% Black", col = "gold")+
  tm_format_NLD()
# close the png file
dev.off()