geom_stars function

ggplot geom for stars objects

geom_stars(
  mapping = NULL,
  data = NULL,
  ...,
  downsample = 0,
  sf = FALSE,
  na.action = na.pass
)

theme_stars(...)

Arguments

• mapping: see geom_raster
• data: see geom_raster
• ...: see geom_raster
• downsample: downsampling rate: e.g. 3 keeps rows and cols 1, 4, 7, 10 etc.; a value of 0 does not downsample; can be specified for each dimension, e.g. c(5,5,0) to downsample the first two dimensions but not the third.
• sf: logical; if TRUE rasters will be converted to polygons and plotted using geom_sf .
• na.action: function; if NA values need to be removed before plotting use the value na.omit here (only applies to objects with raster dimensions)

Details

geom_stars returns (a call to) either geom_raster , geom_tile , or geom_sf , depending on the raster or vector geometry; for the first to, an aes call is constructed with the raster dimension names and the first array as fill variable. Further calls to coord_equal and facet_wrap are needed to control aspect ratio and the layers to be plotted; see examples. If a stars array contains hex color values, and no fill parameter is given, the color values are used as fill color; see the example below.

If visual artefacts occur (Moiré-Effekt), then see the details section of plot.stars

Examples

system.file("tif/L7_ETMs.tif", package = "stars") %>% read_stars() -> x
if (require(ggplot2, quietly = TRUE)) {
  ggplot() + geom_stars(data = x) +
    coord_equal() +
    facet_wrap(~band) +
    theme_void() +
    scale_x_discrete(expand=c(0,0))+
    scale_y_discrete(expand=c(0,0))
  # plot rgb composite:
  st_as_stars(L7_ETMs)[,,,1:3] |> st_rgb() -> x # x contains colors as pixel values
  ggplot() + geom_stars(data = x)
}