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Plot RGB rasters in ggplot2

Source: R/geom_spatial_rgb.R
geom_spatial_rgb.Rd

geom_spatial_rgb and stat_spatial_rgb allow users to plot three-band RGB rasters in ggplot2, using these layers as background base maps for other spatial plotting. Note that unlike ggplot2::geom_sf, this function does not force ggplot2::coord_sf; for accurate mapping, add ggplot2::coord_sf with a crs value matching your input raster as a layer.

Usage

geom_spatial_rgb(
  mapping = NULL,
  data = NULL,
  stat = "spatialRGB",
  position = "identity",
  ...,
  hjust = 0.5,
  vjust = 0.5,
  interpolate = FALSE,
  na.rm = FALSE,
  show.legend = NA,
  inherit.aes = TRUE,
  scale = NULL
)

stat_spatial_rgb(
  mapping = NULL,
  data = NULL,
  geom = "raster",
  position = "identity",
  na.rm = FALSE,
  show.legend = FALSE,
  inherit.aes = TRUE,
  scale = NULL,
  ...
)

Arguments

mapping

Set of aesthetic mappings created by 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

The data to be displayed in this layer. In addition to the three options described in ggplot2::geom_raster, there are two additional methods:

If a SpatRaster object (see terra::rast), this function will coerce the raster to a data frame and assume the raster bands are in RGB order (while allowing for, but ignoring, a fourth alpha band).

If a length-1 character vector, this function will attempt to load the object via terra::rast.

stat

The statistical transformation to use on the data for this layer, either as a ggproto Geom subclass or as a string naming the stat stripped of the stat_ prefix (e.g. "count" rather than "stat_count")

position

Position adjustment, either as a string naming the adjustment (e.g. "jitter" to use position_jitter), or the result of a call to a position adjustment function. Use the latter if you need to change the settings of the adjustment.

...

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.

hjust, vjust

horizontal and vertical justification of the grob. Each justification value should be a number between 0 and 1. Defaults to 0.5 for both, centering each pixel over its data location.

interpolate

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

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().

scale

Integer. Maximum (possible) value in the three channels. If NULL, attempts to infer proper values from data -- if all RGB values are <= 1 then 1, <= 255 then 255, and otherwise 65535.

geom

The geometric object to use to display the data, either as a ggproto Geom subclass or as a string naming the geom stripped of the geom_ prefix (e.g. "point" rather than "geom_point")

See also

Other visualization functions: combine_overlays(), raster_to_raw_tiles(), vector_to_overlay()

Examples

if (FALSE) {

simulated_data <- data.frame(
  id = seq(1, 100, 1),
  lat = runif(100, 44.04905, 44.17609),
  lng = runif(100, -74.01188, -73.83493)
)

simulated_data <- sf::st_as_sf(simulated_data, coords = c("lng", "lat"))
simulated_data <- sf::st_set_crs(simulated_data, 4326)

output_tiles <- get_tiles(simulated_data,
  services = c("ortho"),
  resolution = 120
)

merged_ortho <- tempfile(fileext = ".tif")
merge_rasters(output_tiles[["ortho"]], merged_ortho)

merged_stack <- terra::rast(merged_ortho)

library(ggplot2)

ggplot() +
  geom_spatial_rgb(
    data = merged_ortho,
    mapping = aes(
      x = x,
      y = y,
      r = red,
      g = green,
      b = blue
    )
  ) +
  geom_sf(data = simulated_data) +
  coord_sf(crs = 4326)

ggplot() +
  geom_spatial_rgb(
    data = merged_stack,
    mapping = aes(
      x = x,
      y = y,
      r = red,
      g = green,
      b = blue
    )
  ) +
  geom_sf(data = simulated_data) +
  coord_sf(crs = 4326)
}