Figure 3.10 Raster aggregation and disaggregation

figures
code
R

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

Code
library(terra)
library(tmap)
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(breaks = seq(180, 280, 10), 
            palette = "BrBG") + 
  tm_layout(frame = FALSE, legend.show = FALSE)

m2 <- tm_shape(z10) + 
  tm_raster(breaks = seq(180, 280, 10), 
            palette = "BrBG") + 
  tm_layout(frame = FALSE, legend.show = FALSE)

m3 <- tm_shape(z_dash) + 
  tm_raster(breaks = seq(180, 280, 10), 
            palette = "BrBG", style = "fixed") + 
  tm_layout(frame = FALSE, legend.show = FALSE)

tmap_arrange(m1, m2, m3)

Code
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