Visibility graphs

Primary reference: Lacasa et al. (2008) Proc. Natl. Acad. Sci. 105, 4972–4975.

Horizontal (HVG) and natural (NVG) visibility graphs connect time samples when no intermediate sample blocks line-of-sight visibility in the time-amplitude plane.

Assumptions

  • Samples are ordered and equally spaced (or treated as such).

  • Mean HVG degree ≈ 4 for i.i.d. random series (literature fixture: hvg_mean_degree_gaussian).

  • Strictly monotone series form a consecutive chain (hvg_monotone_edges).

Directed irreversibility

Reference: Lacasa et al. (2012) Sci. Rep. 2, 378.

visibility_irreversibility() compares forward vs reversed visibility statistics. Asymmetric ramps should yield positive irreversibility scores.

API