metricT - Directional Fragility Diagnostics for EEG Connectivity

Implements Metric-T, a permutation-based diagnostic that flags when the reported direction of a group difference in electroencephalography (EEG) functional connectivity depends on the choice of metric. Direction consistency (DC) converts the weighted phase lag index (wPLI) and magnitude-squared coherence (MSC), both derived from the same cross-spectrum, into the percentage of channel-pair features for which one group exceeds the other; Metric-T is T = DC(wPLI) - DC(MSC). Significance is assessed by aligned label permutation with marginal and Westfall-Young max-T multiplicity control. For small samples the reference set is enumerated completely: exact two-group tests, the complete two-group labelling space (in which cut-points, exclusions and batches are located on one distribution), and a stratified exact test for a continuous covariate. Core functions use base R only; a 'shiny' graphical interface is included. Method: Kimura (2026) <doi:10.1016/j.neuri.2026.100286>.