plot stars object, with subplots for each level of first non-spatial dimension

plot stars object, with subplots for each level of first non-spatial dimension, and customization of legend key

# S3 method for stars
plot(
  x,
  y,
  ...,
  join_zlim = TRUE,
  main = make_label(x, 1),
  axes = FALSE,
  downsample = TRUE,
  nbreaks = 11,
  breaks = "quantile",
  col = grey(1:(nbreaks - 1)/nbreaks),
  key.pos = get_key_pos(x, ...),
  key.width = lcm(1.8),
  key.length = 0.618,
  reset = TRUE,
  box_col = grey(0.8),
  center_time = FALSE,
  hook = NULL,
  mfrow = NULL
)

# S3 method for stars
image(
  x,
  ...,
  band = 1,
  attr = 1,
  asp = NULL,
  rgb = NULL,
  maxColorValue = ifelse(inherits(rgb, "data.frame"), 255, max(x[[attr]], na.rm = TRUE)),
  xlab = if (!axes) "" else names(d)[1],
  ylab = if (!axes) "" else names(d)[2],
  xlim = st_bbox(extent)$xlim,
  ylim = st_bbox(extent)$ylim,
  text_values = FALSE,
  text_color = "black",
  axes = FALSE,
  interpolate = FALSE,
  as_points = FALSE,
  key.pos = NULL,
  logz = FALSE,
  key.width = lcm(1.8),
  key.length = 0.618,
  add.geom = NULL,
  border = NA,
  useRaster = isTRUE(dev.capabilities()$rasterImage == "yes"),
  extent = x
)

# S3 method for nc_proxy
plot(x, y, ..., downsample = get_downsample(dim(x)), max_times = 16)

# S3 method for stars_proxy
plot(x, y, ..., downsample = get_downsample(dim(x)))

Arguments

x: object of class stars
y: ignored
...: further arguments: for plot, passed on to image.stars; for image, passed on to image.default or rasterImage.
join_zlim: logical; if TRUE, compute a single, joint zlim (color scale) for all subplots from x
main: character; subplot title prefix; use "" to get only time, use NULL to suppress subplot titles
axes: logical; should axes and box be added to the plot?
downsample: logical or numeric; if TRUE will try to plot not many more pixels than actually are visible, if FALSE, no downsampling takes place, if numeric, the number of pixels/lines/bands etc that will be skipped; see Details.
nbreaks: number of color breaks; should be one more than number of colors. If missing and col is specified, it is derived from that.
breaks: actual color breaks, or a method name used for classIntervals.
col: colors to use for grid cells, or color palette function
key.pos: integer; side to plot a color key: 1 bottom, 2 left, 3 top, 4 right; set to NULL to omit key. Ignored if multiple columns are plotted in a single function call. Default depends on plot size, map aspect, and, if set, parameter asp.
key.width: amount of space reserved for width of the key (labels); relative or absolute (using lcm)
key.length: amount of space reserved for length of the key (labels); relative or absolute (using lcm)
reset: logical; if FALSE, keep the plot in a mode that allows adding further map elements; if TRUE restore original mode after plotting
box_col: color for box around sub-plots; use 0 to suppress plotting of boxes around sub-plots.
center_time: logical; if TRUE, sub-plot titles will show the center of time intervals, otherwise their start
hook: NULL or function; hook function that will be called on every sub-plot; see examples.
mfrow: length-2 integer vector with nrows, ncolumns of a composite plot, to override the default layout
band: integer; which band (dimension) to plot
attr: integer; which attribute to plot
asp: numeric; aspect ratio of image
rgb: integer; specify three bands to form an rgb composite. Experimental: rgb color table; see Details.
maxColorValue: numeric; passed on to rgb
xlab: character; x axis label
ylab: character; y axis label
xlim: x axis limits
ylim: y axis limits
text_values: logical; print values as text on image?
text_color: character; color for printed text values
interpolate: logical; when using rasterImage (rgb), should pixels be interpolated?
as_points: logical; for curvilinear or sheared grids: parameter passed on to st_as_sf, determining whether raster cells will be plotted as symbols (fast, approximate) or small polygons (slow, exact)
logz: logical; if TRUE, use log10-scale for the attribute variable. In that case, breaks and at need to be given as log10-values; see examples.
add.geom: object of class sfc, or list with arguments to plot, that will be added to an image or sub-image
border: color used for cell borders (only in case x is a curvilinear or rotated/sheared grid)
useRaster: logical; use the rasterImage capabilities of the graphics device?
extent: object which has a st_bbox method; sets the plotting extent
max_times: integer; maximum number of time steps to attempt to plot.

Details

Downsampling: a value for downsample of 0: no downsampling, 1: after every dimension value (pixel/line/band), one value is skipped (half of the original resolution), 2: after every dimension value, 2 values are skipped (one third of the original resolution), etc.

To remove unused classes in a categorical raster, use the droplevels function.

When bitmaps show visual artefacts (Moiré effects), make sure that device png is used rather than ragg::agg_png as the latter uses antialiasing for filled polygons which causes this; see also https://github.com/r-spatial/stars/issues/573 .

use of an rgb color table is experimental; see https://github.com/r-spatial/mapview/issues/208

when plotting a subsetted stars_proxy object, the default value for argument downsample will not be computed correctly, and has to be set manually.

Examples

st_bbox(L7_ETMs) |> st_as_sfc() |> st_centroid() |> st_coordinates() -> pt
hook1 = function() {
    text(pt[,"X"], pt[,"Y"], "foo", col = 'orange', cex = 2)
}
plot(L7_ETMs, hook = hook1)

x = st_set_dimensions(L7_ETMs, 3, paste0("B_", 1:6))
hook2 = function(..., row, col, nr, nrow, ncol, value, bbox) {
   str = paste0("row ", row, "/", nrow, ", col ", col, "/", ncol, "\nnr: ", nr, " value: ", value)
   bbox |> st_as_sfc() |> st_centroid() |> st_coordinates() -> pt
   text(pt[,"X"], pt[,"Y"], str, col = 'red', cex = 2)
}
plot(x, hook = hook2, col = grey(c(.2,.25,.3,.35)))

tif = system.file("tif/L7_ETMs.tif", package = "stars")
x = read_stars(tif)
image(x, col = grey((3:9)/10))

image(x, rgb = c(1,3,5)) # rgb composite
#> Error in image.stars(x, rgb = c(1, 3, 5)): rgb plotting not supported on this device