Computes end-point degrees for a bipartite network
Computes end-point degrees for a bipartite network, following the suggestion of Barrat et al. (2004)
endpoint(web)
web |
A matrix with pollinators as columns and plants as rows. Alternatively, when used on e.g. species occurrences across islands, rows are islands. |
Computation follows the outline of Gitarranz et al. (2004): “the product k_i k_j of the degree of the two nodes connected by that link”. We then set additionally endpoint degrees for all non-existing links to 0! Thus, only for existing links endpoint degrees are computed. This is (to me) not obvious from the description in Gitarranz et al. (2004).
A matrix of end-point degrees
This approach is, AFAIK, not tested by simulation; whether it is useful has still to be shown.
Carsten F. Dormann
Barrat, A., M. Barthélemy, R. Pastor-Satorras, and A. Vespignani. 2004. The architecture of complex weighted networks. Proceedings of the National Academy of Sciences of the USA 101, 3747-–3752. doi: 10.1073/pnas.0400087101.
Gilarranz, L. J., J. M. Pastor, and J. Galeano. 2011. The architecture of weighted mutualistic networks. Oikos 121, 1154–-1162. doi: 10.1111/j.1600-0706.2011.19592.x.
# reproduces the example of Gitarranz et al. (2011): data(memmott1999) ends <- endpoint(memmott1999) weights.mean <- tapply(memmott1999, ends, mean) ends.weights <- tapply(ends, ends, mean) plot(weights.mean, ends.weights, log="xy", pch=16)
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