Figure 3.10 Raster aggregation and disaggregation

figures

code

This figure shows how you can’t recover raster information after aggregation.

Code

library(terra)
library(tmap)
library(cols4all)
library(dplyr)

Get the data—you’ll need some of your own data here.

Code

z <- rast("raster-data.tif")

Aggregate and disaggregate by 10

Code

z10 <- z |> 
  aggregate(10)

z_dash <- z10 |>
  resample(z)

Make maps. For the images in the book, I dissolved the raster layers to polygons to create smaller SVG outputs that I was better able to control in making final graphics. For online, I don’t need to worry about that.

Code

m1 <- tm_shape(z) + 
  tm_raster(
    col.scale = tm_scale(breaks = seq(180, 280, 10),
                         values = "brewer.br_bg")) + 
  tm_layout(frame = FALSE, legend.show = FALSE)

m2 <- tm_shape(z10) + 
  tm_raster(
    col.scale = tm_scale(breaks = seq(180, 280, 10),
                         values = "brewer.br_bg")) + 
  tm_layout(frame = FALSE, legend.show = FALSE)

m3 <- tm_shape(z_dash) + 
  tm_raster(
    col.scale = tm_scale(breaks = seq(180, 280, 10),
                         values = "brewer.br_bg")) + 
  tm_layout(frame = FALSE, legend.show = FALSE)

tmap_arrange(m1, m2, m3)

Code

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