tidyterra (version 0.1.0)

geom_spatraster: Visualise SpatRaster objects

Description

This geom is used to visualise SpatRaster objects (see terra::rast()). The geom is designed for visualise the object by layers, as terra::plot() does.

For plotting SpatRaster objects as map tiles (i.e. RGB SpatRaster), use geom_spatraster_rgb().

The underlying implementation is based on ggplot2::geom_raster().

Usage

geom_spatraster(
  mapping = aes(),
  data,
  na.rm = TRUE,
  show.legend = NA,
  inherit.aes = FALSE,
  interpolate = FALSE,
  maxcell = 5e+05,
  ...
)

Arguments

mapping

Set of aesthetic mappings created by aes() or aes_(). If specified and inherit.aes = TRUE (the default), it is combined with the default mapping at the top level of the plot. You must supply mapping if there is no plot mapping.

data

A SpatRaster object.

na.rm

If FALSE, the default, missing values are removed with a warning. If TRUE, missing values are silently removed.

show.legend

logical. Should this layer be included in the legends? NA, the default, includes if any aesthetics are mapped. FALSE never includes, and TRUE always includes. It can also be a named logical vector to finely select the aesthetics to display.

inherit.aes

If FALSE, overrides the default aesthetics, rather than combining with them. This is most useful for helper functions that define both data and aesthetics and shouldn't inherit behaviour from the default plot specification, e.g. borders().

interpolate

If TRUE interpolate linearly, if FALSE (the default) don't interpolate.

maxcell

positive integer. Maximum number of cells to use for the plot.

...

Other arguments passed on to layer(). These are often aesthetics, used to set an aesthetic to a fixed value, like colour = "red" or size = 3. They may also be parameters to the paired geom/stat.

Value

A ggplot2 layer

terra equivalent

terra::plot()

Coords

When the SpatRaster does not present a crs (i.e., terra::crs(rast) == "") the geom does not make any assumption on the scales.

On SpatRaster that have a crs, the geom uses ggplot2::coord_sf() to adjust the scales. That means that also the SpatRaster may be reprojected.

Aesthetics

geom_spatraster() understands the following aesthetics:

• fill

If fill is not provided, geom_spatraster() creates a ggplot2 layer with all the layers of the SpatRaster object. Use facet_wrap(~lyr) to display properly the SpatRaster layers.

If fill is used, it should contain the name of one layer that is present on the SpatRaster (i.e. geom_spatraster(data = rast, aes(fill = <name_of_lyr>)). Names of the layers can be retrieved using names(rast).

Facets

You can use facet_wrap(~lyr) for creating a faceted plot by each layer of the SpatRaster object. See ggplot2::facet_wrap() for details.

Computed variables

This geom computes internally some variables that are available for use as aesthetics, using (for example) aes(color = after_stat(<computed>)) (see ggplot2::after_stat()).

lyr

Name of the layer.

See Also

ggplot2::geom_raster(), ggplot2::coord_sf(), ggplot2::facet_wrap()

Other ggplot2 utils: autoplot(), geom_spat_contour, geom_spatraster_rgb(), ggspatvector, scale_fill_terrain

Examples

# NOT RUN {
# Avg temperature on spring in Castille and Leon (Spain)
file_path <- system.file("extdata/cyl_temp.tif", package = "tidyterra")

library(terra)
temp_rast <- rast(file_path)

library(ggplot2)

# Display a single layer
names(temp_rast)

ggplot() +
  geom_spatraster(data = temp_rast, aes(fill = tavg_04)) +
  # You can use coord_sf
  coord_sf(crs = 3857) +
  scale_fill_terrain_c()

# Display facets
ggplot() +
  geom_spatraster(data = temp_rast) +
  facet_wrap(~lyr, ncol = 2) +
  scale_fill_terrain_b()


# Non spatial rasters

no_crs <- rast(crs = NA, extent = c(0, 100, 0, 100), nlyr = 1)
values(no_crs) <- seq_len(ncell(no_crs))


ggplot() +
  geom_spatraster(data = no_crs)

# Downsample

ggplot() +
  geom_spatraster(data = no_crs, maxcell = 25)
# }
# NOT RUN {
# }