Measure mental-map stability between two layouts

Compares region centroids before and after a transition and reports how far regions drifted. Use it to confirm that expanding one branch left the rest of the map stable: pass the non-expanded (sibling) regions as before and after. Lower drift means the user's mental map survived.

Usage

layout_metrics(before, after, id_col)

Arguments

before

An sf object with the layout before the transition.

after

An sf object with the layout after the transition.

id_col

Column present in both objects identifying each region.

Value

A named list with mean_drift and max_drift (map units), stability (0-100; 100 means no drift, 0 means mean drift of one third of the before bounding-box diagonal or more), and n_matched (regions compared). Regions missing from after are dropped with a warning.

See also

build_elastic_transition().

Examples

rect <- function(x0, x1, y0, y1) {
  sf::st_polygon(list(cbind(c(x0, x1, x1, x0, x0), c(y0, y0, y1, y1, y0))))
}
before <- sf::st_sf(
  region = c("A", "B"),
  geometry = sf::st_sfc(rect(0, 1, 0, 1), rect(2, 3, 0, 1), crs = 3857)
)
after <- before
sf::st_geometry(after)[2] <- sf::st_geometry(after)[[2]] + c(0.5, 0)
layout_metrics(before, after, id_col = "region")
#> $mean_drift
#> [1] 0.25
#> 
#> $max_drift
#> [1] 0.5
#> 
#> $stability
#> [1] 76
#> 
#> $n_matched
#> [1] 2
#>