NA values are shown in gray color

[Nowosad]

NA values are removed in the package examples; however, they are shown in gray color in my case:

library(tidyterra)
library(ggplot2)
library(terra)
nz_elev = rast(system.file("raster/nz_elev.tif", package = "spDataLarge"))

ggplot() + 
  geom_spatraster(data = nz_elev)
#> SpatRaster resampled to ncells = 501147

^{Created on 2022-07-07 by the reprex package (v2.0.1)}

[dieghernan]

HI @Nowosad !

Plotting NAs is the default behaviour on ggplot2, that plots NAs with grey50.

On the examples I think I used tidyterra::scale_fill_*. These scales differs of the default ggplot2 scales on an option, na.value, that have been set to NA. This prevents NAs from being plotted, but still can be manipulated. Hope this reprex provides clarity:

library(tidyterra)
#> ── Attaching packages ─────────────────────────────────────── tidyterra 0.2.0 ──
#> 
#> Suppress this startup message by setting Sys.setenv(tidyterra.quiet = TRUE)
#> ✔ tibble 3.1.6     ✔ dplyr  1.0.7
#> ✔ tidyr  1.1.4
library(ggplot2)
library(terra)
#> terra 1.5.34
#> 
#> Attaching package: 'terra'
#> The following object is masked from 'package:tidyr':
#> 
#>     extract

nz_elev <- rast(system.file("raster/nz_elev.tif", package = "spDataLarge"))

ggplot() +
  geom_spatraster(data = nz_elev)
#> SpatRaster resampled to ncells = 501147

# The underlying default scale is this
ggplot() +
  geom_spatraster(data = nz_elev) +
  scale_fill_continuous(na.value = "grey50")
#> SpatRaster resampled to ncells = 501147

# Avoid plotting NAs with this
ggplot() +
  geom_spatraster(data = nz_elev) +
  scale_fill_continuous(na.value = NA)
#> SpatRaster resampled to ncells = 501147

# The scales of tidyterra has na.value = NA by default, so NAs are not plotted
ggplot() +
  geom_spatraster(data = nz_elev) +
  scale_fill_whitebox_c()
#> SpatRaster resampled to ncells = 501147

# But his value can be manipulated
ggplot() +
  geom_spatraster(data = nz_elev) +
  scale_fill_whitebox_c(na.value = "lightblue1")
#> SpatRaster resampled to ncells = 501147

^{Created on 2022-07-07 by the reprex package (v2.0.1)}

[dieghernan]

For completitude, the default on terra::plot() is colNA = NULL (equivalent to na.value=NA in ggplot2) , while the default in ggplot2 is na.value="grey50") (equivalent to terra::plot(colNA="grey50"):

library(tidyterra)
library(terra)
nz_elev <- rast(system.file("raster/nz_elev.tif", package = "spDataLarge"))

ramp <- colorRampPalette(c("#132B43","#56B1F7"))

# The default on terra::plot is not plotting NAs
plot(nz_elev, col=ramp(100))

# While this would be the default on ggplot2
plot(nz_elev, col=ramp(100), colNA="grey50")

^{Created on 2022-07-07 by the reprex package (v2.0.1)}

[Nowosad]

Thanks a lot for the explanation, @dieghernan !

[dieghernan]

Hi @Nowosad, it seems that for SpatRasters with a large amount of NA it is safer to use na.value = "transparent", see #120