Check Geographic Representativeness of CV Folds — borg_check

Evaluates whether each fold's test set covers a representative portion of the study area. Flags folds that are geographically isolated or biased toward one region.

Usage

borg_check_coverage(folds, data, coords, threshold = 0.2)

Arguments

folds: A borg_cv object or list of fold lists.
data: Data frame with coordinate columns.
coords: Character vector of length 2. Coordinate column names.
threshold: Numeric. Minimum proportion of geographic extent that each fold should cover (0-1). Default: 0.2 (each fold covers at least 20 percent of the x and y extent).

Value

A data frame with class "borg_geo_strat" containing per-fold coverage metrics:

fold: Fold index
x_coverage: Proportion of x-extent covered by test set
y_coverage: Proportion of y-extent covered by test set
area_ratio: Convex hull area ratio (test / total)
centroid_x, centroid_y: Test set centroid
balanced: Whether fold meets the threshold

Examples

set.seed(42)
d <- data.frame(x = runif(200, 0, 100), y = runif(200, 0, 100), z = rnorm(200))
cv <- borg_cv(d, coords = c("x", "y"), target = "z")
strat <- borg_check_coverage(cv, d, coords = c("x", "y"))
strat