geocompr: Geocomputation with R

library(tmap)
library(terra)
multi_raster_file = system.file("raster/landsat.tif", package = "spDataLarge")
multi_rast = rast(multi_raster_file)
multi_rast = (multi_rast * 0.0000275) - 0.2
multi_rast[multi_rast < 0] = 0
ndvi_fun = function(nir, red){
  (nir - red) / (nir + red)
}
ndvi_rast = lapp(multi_rast[[c(4, 3)]], fun = ndvi_fun)
multi_rast2 = stretch(multi_rast, maxq = 0.98)

tm1 = tm_shape(multi_rast2[[3:1]]) +
  tm_rgb(tm_mv("landsat_3", "landsat_2", "landsat_1"), col.scale = tm_scale_rgb(maxValue = 255)) +
  tm_title("RGB image") +
  tm_layout(frame = FALSE)
tm2 = tm_shape(ndvi_rast) +
  tm_raster(col.scale = tm_scale_continuous(), col.legend = tm_legend(title = "", reverse = TRUE, text.size = 0.5)) +
  tm_title("NDVI") +
  tm_layout(frame = FALSE,
            legend.frame = TRUE,
            legend.position = c("left", "bottom"),
            legend.bg.color = "white")
tma = tmap_arrange(tm1, tm2, nrow = 1)
tmap_save(tma, "images/04-ndvi.png", height = 800*2, width = 1100*2)