plot.controlledburn: Plot a burn

In controlledburn: Sparse Geometry Rasterization with Exact Coverage Fractions

Plot a burn

Description

Draw a burn() result in map coordinates (asp = 1) with the grid extent as the frame. Two renderings are available:

Usage

## S3 method for class 'controlledburn'
plot(
  x,
  what = c("auto", "exact", "overview"),
  marginals = TRUE,
  col = grDevices::hcl.colors(64, "YlOrRd", rev = TRUE),
  by_id = FALSE,
  tiles = 256L,
  threshold = 50000,
  content = FALSE,
  main = NULL,
  ...
)

Arguments

x	A controlledburn object returned by burn().
what	"auto", "exact", or "overview".
marginals	Draw the row and column marginal strips. The layout is sized from the extent's aspect ratio so the strips span exactly the map; leftover device space is left blank.
col	Colour ramp (low to high coverage) for "overview" and for edge shading in "exact".
by_id	In "exact" mode, colour cells by geometry id instead of by coverage (edge cells take their fraction as opacity).
tiles	Passed to overview_burn() for the "overview" rendering.
threshold	Record count above which "auto" switches to "overview".
content	Draw the content extent (bounding box of touched cells) as a dashed rectangle.
main	Optional title, drawn in the outer margin above the strips.
...	Passed to graphics::plot() for the main panel.

Details

"exact"

every record is drawn: runs as rectangles, edge cells shaded by coverage fraction, line cells shaded by length (relative to the cell diagonal), points as cells. Cost is one rectangle per record, so this is the picture of the sparse representation itself.

"overview"

the coarse mean-coverage matrix from overview_burn() drawn with ximage::ximage(). Cost does not depend on grid size.

"auto" (default) picks "exact" when the total record count is at most threshold, else "overview". Either way the optional marginal strips are exact: covered cells per grid row (right) and per grid column (top), from summary.controlledburn().

Value

x, invisibly, with the summary computed for the marginals attached as attribute summary.

Examples

if (requireNamespace("geos", quietly = TRUE)) {
  poly <- geos::as_geos_geometry(c("POLYGON ((1 1, 9 1, 9 9, 1 9, 1 1))",
                                   "POLYGON ((2 2, 4 3, 3 5, 2 2))"))
  r <- burn(poly, extent = c(0, 10, 0, 10), dimension = c(40L, 40L))
  plot(r)
  plot(r, by_id = TRUE, marginals = FALSE)
  plot(r, what = "overview", tiles = 10)
}

controlledburn documentation built on Oct. 28, 2026, 5:12 p.m.