Legend of a raster map with categorical data

Question

I would like to plot a raster containing 4 different values (1) with a categorical text legend describing the categories such as 2 but with colour boxes:

I\'ve tried

Answer 1

By default, the colours used in a raster-plot are generated by rev(terrain.colors()) (see ?raster::plot). You can use this to re-create that sequence of 4 colours for your legend - or choose a random sequence of colours:

my_col = rev(terrain.colors(n = 4))
# my_col = c('beige','red','green','blue')

First plot the map using the colour sequence. legend = FALSE gets rid of the standard colour bar:

plot(my_raster, legend = FALSE, col = my_col)

Add a custom legend to the bottom left. Use the fill argument to generate coloured boxes:

legend(x='bottomleft', legend = c("land", "ocean/lake", "rivers", "water bodies"), fill = my_col)