genAldousBetaTree - Generates a rooted binary tree in
phylo format with the given number of n leaves under the
Aldous beta model.
The Aldous beta model is not a rate-based incremental evolutionary (tree)
construction and thus cannot generate edge lengths, only a topology.
Instead, the Aldous beta model works as follows: The idea is to start with
the root and the set of its descendant leaves, i.e., all n leaves.
Then, this set is partitioned into two subsets according to a density
function dependent on the parameter beta.
The two resulting subsets contain the leaves of the two maximal pending
subtrees of the root, respectively. The same procedure is then applied to the
root's children and their respective subsets, and so forth.
genAldousBetaTree(n, BETA)genAldousBetaTree A single tree of class phylo is
returned.
Integer value that specifies the desired number of leaves, i.e.,
vertices with in-degree 1 and out-degree 0.
Due to the restrictions of the phylo or multiphylo format,
the number of leaves must be at least 2 since there must be at
least one edge.
Numeric value >=-2 which specifies how the leaf sets
are partitioned. For certain choices of BETA the Aldous beta model
coincides with known models:
BETA = 0: Yule model
BETA = -3/2: PDA model (all phylogenies equally probable)
BETA = -2: Caterpillar with n leaves
D. Aldous. Probability Distributions on Cladograms. In Random Discrete Structures, pages 1–18. Springer New York, 1996.
genAldousBetaTree(n = 5, BETA = 1)
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