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Ink and overplotting statistics for a scene

Source: R/analysis.R
scene_stats.Rd

How much of the canvas a scene actually covers, and how hard it is working to do it. overplot is the honest signal for "should this be datashade()-ed?": a count of marks says nothing about whether they overlap, whereas thirty thousand well-separated points are fine and eight thousand piled on top of each other are not.

Usage

scene_stats(scene)

Arguments

scene

A vl_scene(), or anything with an as_vellum_scene() method.

Value

A one-row data frame:

elements

total drawn elements.

ink

fraction of canvas pixels differing from the background.

colours

distinct colours in the rendered image.

overplot

summed element-box area divided by inked area — an estimate of how many times an average inked pixel was drawn over. 1 means no overlap. It is computed from bounding boxes, so it over-estimates for non-rectangular marks (a circle fills ~79% of its box); treat it as an index, not a measurement. Marks the element table does not cover — text, and unkeyed lines/polygons/paths — contribute to ink but not to overplot.

See also

vl_lint(), profile_render(), datashade()

Examples

set.seed(1)
sparse <- vl_scene(4, 3) |> draw(points_grob(runif(200), runif(200)))
dense <- vl_scene(4, 3) |> draw(points_grob(rnorm(20000, 0.5, 0.05),
                                            rnorm(20000, 0.5, 0.05)))
rbind(sparse = scene_stats(sparse), dense = scene_stats(dense))
#>        elements       ink colours   overplot
#> sparse      200 0.1416016     256   2.918994
#> dense     20000 0.1258681     256 328.386864