Compute spatial cluster sizes of extreme events

For each time step, counts the land cells where the hazard value meets or exceeds threshold. This is the cluster-size metric \(B(t)\) (Eq. 21, Appendix C of Clavijo Mesa et al., 2026) used to validate whether a dependence model reproduces the observed spatial footprint.

Usage

hm_cluster_size(X, threshold, time = NULL)

Arguments

X

Numeric matrix (\(T \times N\)) from [hm_filter_land_cells()].

threshold

A single finite numeric value.

time

Optional date vector of length \(T\). Defaults to row indices.

Value

A data.frame with columns date, cluster_size, and cluster_fraction.

References

Clavijo Mesa, M.V., Di Maio, F. & Zio, E. (2026). Reliability Engineering & System Safety, 275, 112830.

See also

[hm_filter_land_cells()], [hm_select_extreme_events()]

Examples

if (FALSE) { # \dontrun{
X_land <- hm_filter_land_cells(X)
cs     <- hm_cluster_size(X_land, threshold = 25,
                           time = attr(X_land, "time"))
summary(cs$cluster_size)
} # }