Package {treebalance}

Title:	Computation of Tree (Im)Balance Indices
Version:	1.2.2
Description:	The aim of the 'R' package 'treebalance' is to provide functions for the computation of a large variety of (im)balance indices for rooted trees. The package accompanies the book ”Tree Balance Indices - A Comprehensive Survey” by M. Fischer, L. Herbst, S. Kersting, L. Kuehn and K. Wicke (2023) <doi:10.1007/978-3-031-39800-1>, which gives a precise definition for the terms 'balance index' and 'imbalance index' (Chapter 4) and provides an overview of the terminology in this manual (Chapter 2). For further information on (im)balance indices, see also Fischer et al. (2021) https://treebalance.wordpress.com. Considering both established and new (im)balance indices, 'treebalance' provides (among others) functions for calculating the following 18 established indices and index families: the average leaf depth, the B1 and B2 index, the Colijn-Plazzotta rank, the normal, corrected, quadratic and equal weights Colless index, the family of Colless-like indices, the family of I-based indices, the Rogers J index, the Furnas rank, the rooted quartet index, the s-shape statistic, the Sackin index, the symmetry nodes index, the total cophenetic index and the variance of leaf depths. Additionally, we include 6 tree shape statistics that satisfy the definition of an (im)balance index but have not been thoroughly analyzed in terms of tree balance in the literature yet. These are: the maximum width, the modified maximum difference in widths, the maximum depth, the maximum width over maximum depth, the stairs1 and the stairs2 index. As input, most functions of 'treebalance' require a rooted (phylogenetic) tree in 'phylo' format (as introduced in 'ape' 1.9 in November 2006). 'phylo' is used to store (phylogenetic) trees with no vertices of out-degree one. For further information on the format we kindly refer the reader to E. Paradis (2012) https://emmanuelparadis.github.io/misc/FormatTreeR_24Oct2012.pdf.
Depends:	R (≥ 3.5.0)
Imports:	ape, memoise, gmp
License:	GPL-3
Encoding:	UTF-8
LazyData:	true
NeedsCompilation:	no
Config/roxygen2/version:	8.1.0
Packaged:	2026-09-29 14:57:37 UTC; AGFischer
Author:	Mareike Fischer [aut], Lina Herbst [aut], Sophie Kersting [aut, cre], Luise Kuehn [aut], Kristina Wicke [aut]
Maintainer:	Sophie Kersting <treebalanceindices@gmail.com>
Repository:	CRAN
Date/Publication:	2026-10-01 19:00:02 UTC

Calculation of the B1 index for rooted trees

Description

This function calculates the B1 index B1(T) for a given rooted tree T. The tree must not necessarily be binary. B1(T) is defined as

B1(T)=\sum_{u\in V_{in}(T)\setminus\{\rho\}} h(T_u)^{-1}

in which V_{in}(T)\setminus\{\rho\} denotes the set of inner vertices of T without the root, and h(T_u) denotes the height of the pending subtree rooted at u. When restricted to binary trees, the B1 index is a balance index. For arbitrary trees it does not fulfill the definition of an (im)balance index.

For n=1 the function returns B1(T)=0 and a warning.

Usage

B1I(tree)

Arguments

Value

B1I returns the B1 index of the given tree.

Author(s)

Sophie Kersting

References

K.-T. Shao and R. R. Sokal. Tree Balance. Systematic Zoology, 39(3):266, 1990.
doi: 10.2307/2992186.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
B1I(tree)

Calculation of the B2 index for rooted trees

Description

This function calculates the B2 index B2(T) for a given rooted tree T. The tree must not necessarily be binary. B2(T) is defined as

B2(T)=-\sum_{x\in V_L(T)} p_x\cdot log(p_x)

in which V_L(T) denotes the leaf set of T, and in which

p_x=\prod_{v\in anc(x)} \frac{1}{|child(v)|}

denotes the probability of reaching leaf x when starting at the root and assuming equiprobable branching at each vertex v\in anc(x) with anc(x) denoting the set of ancestors of x excluding x. child(v) denotes the set of children of the inner vertex v.
The B2 index is a balance index.

For n=1 the function returns B2(T)=0 and a warning.

Usage

B2I(tree, logbase = 2)

Arguments

Value

B2I returns the B2 index of the given tree.

Author(s)

Sophie Kersting, Luise Kuehn

References

K.-T. Shao and R. R. Sokal. Tree Balance. Systematic Zoology, 39(3):266, 1990.
doi: 10.2307/2992186.

P.-M. Agapow and A. Purvis. Power of Eight Tree Shape Statistics to Detect Nonrandom Diversification: A Comparison by Simulation of Two Models of Cladogenesis. Systematic Biology, 51(6):866-872, 2002.doi: 10.1080/10635150290102564.
URL https://doi.org/10.1080/10635150290102564.

M. Hayati, B. Shadgar, and L. Chindelevitch. A new resolution function to evaluate tree shape statistics. PLOS ONE, 14(11):e0224197, 2019. doi: 10.1371/journal.pone.0224197.
URL https://doi.org/10.1371/journal.pone.0224197.

M. Kirkpatrick and M. Slatkin. Searching for evolutionary patterns in the shape of a phylogenetic tree. Evolution, 47(4):1171-1181, 1993. doi: 10.1111/j.1558-5646.1993.tb02144.x.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
B2I(tree)

Calculation of the I-based indices for rooted trees

Description

This function calculates I-based indices I(T) for a given rooted tree T. Note that the leaves of the tree may represent single species or groups of more than one species. Thus, a vector is required that contains for each leaf the number of species that it represents. The tree may contain few polytomies, which are not allowed to concentrate in a particular region of the tree (see p. 238 in Fusco and Cronk (1995)).

Let v be a vertex of T that fulfills the following criteria: a) The number of descendant (terminal) species of v is k_v>3 (note that if each leaf represents only one species k_v is simply the number of leaves in the pending subtree rooted at v), and b) v has exactly two children.

Then, we can calculate the I_v value as follows:

I_v=\frac{k_{v_a}-\left\lceil\frac{k_v}{2}\right\rceil}{k_v-1-\left\lceil\frac{k_v}{2}\right\rceil}

in which k_{v_a} denotes the number of descendant (terminal) species in the bigger one of the two pending subtrees rooted at v.

As the expected value of I_v under the Yule model depends on k_v, Purvis et al. (2002) suggested to take the corrected values I'_v or I_v^w instead.
The I'_v value of v is defined as follows: I'_v=I_v if k_v is odd and I'_v=\frac{k_v-1}{k_v}\cdot I_v if k_v is even.
The I_v^w value of v is defined as follows:

I_v^w=\frac{w(I_v)\cdot I_v}{mean_{V'(T)} w(I_v)}

where V'(T) is the set of inner vertices of T that have precisely two children and k_v\geq 4, and w(I_v) is a weight function with w(I_v)=1 if k_v is odd and w(I_v)=\frac{k_v-1}{k_v} if k_v is even and I_v>0, and w(I_v)=\frac{2\cdot(k_v-1)}{k_v} if k_v is even and I_v=0.

The I-based index of T can now be calculated using different methods. Here, we only state the version for the I' correction method, but the non-corrected version or the I_v^w corrected version works analogously. 1) root: The I' index of T equals the I'_v value of the root of T, i.e. I'(T)=I'_{\rho}, provided that the root fulfills the two criteria. Note that this method does not fulfil the definition of an (im)balance index. 2) median: The I' index of T equals the median I'_v value of all vertices v that fulfill the two criteria. 3) total: The I' index of T equals the summarised I'_v values of all vertices v that fulfill the two criteria. 4) mean: The I' index of T equals the mean I'_v value of all vertices v that fulfill the two criteria. 5) quartile deviation: The I' index of T equals the quartile deviation (half the difference between third and first quartile) of the I'_v values of all vertices v that fulfill the two criteria.

Usage

IbasedI(
  tree,
  specnum = rep(1, length(tree$tip.label)),
  method = "mean",
  correction = "none",
  logs = TRUE
)

Arguments

Value

IbasedI returns an I-based balance index of the given tree according to the chosen (correction and) method.

Author(s)

Luise Kuehn and Sophie Kersting

References

G. Fusco and Q. C. Cronk. A new method for evaluating the shape of large phylogenies. Journal of Theoretical Biology, 1995. doi: 10.1006/jtbi.1995.0136. URL https://doi.org/10.1006/jtbi.1995.0136.

A. Purvis, A. Katzourakis, and P.-M. Agapow. Evaluating Phylogenetic Tree Shape: Two Modifications to Fusco & Cronks Method. Journal of Theoretical Biology, 2002. doi: 10.1006/jtbi.2001.2443. URL https://doi.org/10.1006/jtbi.2001.2443.

Examples

tree <- ape::read.tree(text="(((((,),),),),);")
IbasedI(tree, method="mean")
IbasedI(tree, method="mean", correction="prime", specnum=c(1,1,2,1,1,1))

Calculation of the area per pair index for rooted trees

Description

This function calculates the area per pair index APP(T) for a given rooted tree T. The tree must not necessarily be binary. APP(T) is defined as

APP(T)=\frac{2}{n\cdot(n-1)}\cdot\sum_{1\leq i<j\leq n} d_T(i,j)

in which n denotes the number of leaves in T, and d_T(i,j) denotes the number of edges on the path between the two leaves i and j. Note that APP(T) can also be computed from the Sackin index S(T) and the total cophenetic index TCI(T) of T as APP(T)=\frac{2}{n}\cdot S(T)-\frac{4}{n(n-1)}\cdot TCI(T) enabling efficient computation.

The area per pair index does not fulfill the definition of an (im)balance index given in "Tree balance indices: a comprehensive survey" (Fischer et al., 2023).

Usage

areaPerPairI(tree)

Arguments

Value

areaPerPairI returns the area per pair index of the given tree.

Author(s)

Luise Kuehn

References

T. Araújo Lima, F. M. D. Marquitti, and M. A. M. de Aguiar. Measuring Tree Balance with Normalized Tree Area. arXiv e-prints, art. arXiv:2008.12867, 2020.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
areaPerPairI(tree)

Calculation of the average leaf depth index for rooted trees

Description

This function calculates the average leaf depth N(T) for a given rooted tree T. The tree must not necessarily be binary. N(T) is defined as

N(T)=\frac{1}{n}\cdot\sum_{u\in V_{in}(T)} n_u

in which n denotes the number of leaves in T, V_{in}(T) denotes the set of inner nodes of T and n_u denotes the number of leaves in the pending subtree that is rooted at the inner node u. Note that N(T) can also be computed from the Sackin index S(T) as N(T)=\frac{1}{n}\cdot S(T). The average leaf depth is an imbalance index.

For n=1 the function returns N(T)=0 and a warning.

Usage

avgLeafDepI(tree)

Arguments

Value

avgLeafDepI returns the average leaf depth of the given tree.

Author(s)

Luise Kuehn

References

M. J. Sackin. "Good" and "Bad" Phenograms. Systematic Biology, 21(2):225-226, 1972. doi: 10.1093/sysbio/21.2.225.

K.-T. Shao and R. R. Sokal. Tree Balance. Systematic Zoology, 39(3):266, 1990.
doi: 10.2307/2992186.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
avgLeafDepI(tree)

Calculation of the average vertex depth for rooted trees

Description

This function calculates the average vertex depth AVD(T) for a given rooted tree T. The tree must not necessarily be binary. AVD(T) is defined as

AVD(T)=\frac{1}{|V(T)|}\cdot\sum_{x\in V(T)} \delta(x)

in which V(T) denotes the set of vertices of T, and \delta(x) denotes the depth of the vertex x. The average vertex depth is an imbalance index.

For n=1 the function returns AVD(T)=0 and a warning.

Usage

avgVertDep(tree)

Arguments

Value

avgVertDep returns the average vertex depth of the given tree.

Author(s)

Luise Kuehn

References

A. Herrada et al. Scaling properties of protein family phylogenies. BMC Evolutionary Biology, 11(1), June 2011. doi: 10.1186/1471-2148-11-155.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,,),),(,)));")
avgVertDep(tree)

Calculation of the cherry index for rooted trees

Description

This function calculates the cherry index ChI(T) for a given rooted tree T. The tree must not necessarily be binary. ChI(T) is defined as the number of cherries in the tree. A cherry is a pair of leaves that have the same direct ancestor. Note, if a vertex u has x leaves as direct descendants, the number of cherries induced by u is binom(x,2).

The cherry index does not fulfill the definition of an (im)balance index given in "Tree balance indices: a comprehensive survey" (Fischer et al., 2023).

Usage

cherryI(tree)

Arguments

Value

cherryI returns the cherry index of the given tree.

Author(s)

Sophie Kersting

References

A. McKenzie and M. Steel. Distributions of cherries for two models of trees. Mathematical Biosciences, 164(1):81-92, 2000. doi: 10.1016/s0025-5564(99)00060-7.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
cherryI(tree)
tree <- ape::read.tree(text="((,),((((,),),),(,)));")
cherryI(tree)
tree <- ape::read.tree(text="((,,,),(,,));")
cherryI(tree)

Calculation of the Colijn-Plazzotta rank for rooted binary trees

Description

This function calculates the Colijn-Plazzotta rank CP(T) for a given rooted binary tree T.

For a binary tree T, the Colijn-Plazzotta rank CP(T) is recursively defined as CP(T)=1 if T consists of only one leaf and otherwise

CP(T)=\frac{1}{2}\cdot CP(T_1)\cdot(CP(T_1)-1)+CP(T_2)+1

with CP(T_1) \geq CP(T_2) being the ranks of the two pending subtrees rooted at the children of the root of T. This rank of T corresponds to its position in the lexicographically sorted list of (i,j): (1),(1,1),(2,1),(2,2),(3,1),... The Colijn-Plazzotta rank of binary trees has been shown to be an imbalance index.

For n=1 the function returns CP(T)=1 and a warning.

Note that the ranks grow very quickly with the number of leaves. Thus, they are computed exactly and returned by default in big.z format (package gmp). With type="double" the function stops for n\geq 10, since the ranks can then no longer be represented exactly as double. The function also stops if the rank would have more than about 5 million digits (e.g. caterpillar trees with more than 27 leaves).

Usage

colPlaLab(tree, type = "bigz")

Arguments

Value

colPlaLab returns the Colijn-Plazzotta rank of the given tree.

Author(s)

Sophie Kersting, Luise Kuehn

References

C. Colijn and G. Plazzotta. A Metric on Phylogenetic Tree Shapes. Systematic Biology, doi: 10.1093/sysbio/syx046.

N. A. Rosenberg. On the Colijn-Plazzotta numbering scheme for unlabeled binary rooted trees. Discrete Applied Mathematics, 2021. doi: 10.1016/j.dam.2020.11.021.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
colPlaLab(tree)
colPlaLab(ape::read.tree(text="((,),(,(,)));"), type="double")

Generation of the rooted binary tree corresponding to a given Colijn-Plazzotta rank

Description

This function generates the unique rooted binary tree T (in phylo format) that corresponds to the given Colijn-Plazzotta rank CP(T). It is the inverse function of colPlaLab().

colPlaLab(): For a given rooted binary tree T, CP(T) is recursively defined as CP(T)=1 if T consists of only one vertex and otherwise CP(T)=\frac{1}{2}\cdot CP(T_1)\cdot(CP(T_1)-1)+CP(T_2)+1 with CP(T_1) \geq CP(T_2) being the ranks of the two pending subtrees rooted at the children of T. The rank CP(T) of T corresponds to its position in the lexicographically sorted list of (i,j): (1),(1,1),(2,1),(2,2),(3,1),...

colPlaLab_inv(): For a given rank CP the corresponding tree T can be reconstructed by starting from one vertex \rho (labelled CP) and recursively splitting vertices whose labels h are greater than 1 into two children with the labels:

i=\left\lceil\frac{1+\sqrt{8\cdot h-7}}{2}\right\rceil-1

and

j=h-\frac{i\cdot(i-1)}{2}-1

until there are no more vertices to split.
For CP=1 the function returns the smallest possible tree in the phylo format: the tree consisting of a single edge.

Note that the ranks grow very quickly with the number of leaves. Thus, the tree is computed with exact integer arithmetic (package gmp); ranks larger than 2^{53} cannot be represented exactly as double and have to be given as bigz or as character.

Usage

colPlaLab_inv(rank)

Arguments

Value

colPlaLab_inv returns the unique rooted binary tree for the given rank.

Author(s)

Sophie Kersting

References

C. Colijn and G. Plazzotta. A Metric on Phylogenetic Tree Shapes. Systematic Biology, 67(1):113-126,2018. doi: 10.1093/sysbio/syx046.

N. A. Rosenberg. On the Colijn-Plazzotta numbering scheme for unlabeled binary rooted trees. Discrete Applied Mathematics, 291:88-98, 2021. doi: 10.1016/j.dam.2020.11.021.

Examples

colPlaLab_inv(22)
colPlaLab_inv("5695183504492614029263280")

Calculation of the Colless index for rooted binary trees

Description

This function calculates variants of the Colless index for a given rooted binary tree T. All of them are imbalance indices.

The original Colless index C(T) is defined as

C(T)=\sum_{u \in V_{in}(T)} |n_{u_a}-n_{u_b}|

in which V_{in}(T) denotes the set of all inner vertices of T, and in which n_{u_a} and n_{u_b} denote the number of leaves in the two pending subtrees that are rooted at the direct descendants of u.

The corrected Colless index I_C(T) of T is defined as I_C(T)=0 for n=1 and n=2 and for n>2 as

I_C(T)=\frac{2\cdot C(T)}{(n-1)\cdot(n-2)}

in which n denotes the total number of leaves in T.

The quadratic Colless index QC(T) of T is defined as

QC(T)=\sum_{u\in V_{in}(T)} |n_{u_a}-n_{u_b}|^2

Special cases: For n=1 the function returns C(T)=I_C(T)=QC(T)=0 and a warning.

Usage

collessI(tree, method = "original")

Arguments

Value

collessI returns the Colless index of the given tree according to the chosen method.

Author(s)

Luise Kuehn and Sophie Kersting

References

D. Colless. Review of Phylogenetics: the theory and practice of phylogenetic systematics. Systematic Zoology, 1982. ISSN 00397989.

T. M. Coronado, M. Fischer, L. Herbst, F. Rosselló, and K. Wicke. On the minimum value of the Colless index and the bifurcating trees that achieve it. Journal of Mathematical Biology, 2020.doi: 10.1007/s00285-020-01488-9.

S. B. Heard. Patterns in tree balance among cladistic, phenetic, and randomly generated phylogenetic trees. Evolution, 1992. doi: 10.1111/j.1558-5646.1992.tb01171.x.

K. Bartoszek, T. M. Coronado, A. Mir, and F. Rosselló. Squaring within the Colless index yields a better balance index. Mathematical Biosciences, 331:108503, 2021. doi: 10.1016/j.mbs.2020.108503.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
collessI(tree, method="original")
collessI(tree, method="corrected")
collessI(tree, method="quadratic")

Calculation of the Colless-like indices for rooted trees

Description

This function calculates the Colless-like index for a given rooted tree T according to the chosen weight function f and dissimilarity D. The Colless-like index CL(T) relative to D and f is the sum of the (D,f)-balance values over all inner vertices of the tree. More precisely,

CL(T)=\sum_{v\in V_{in}(T)} bal_{D,f}(v)

where V_{in}(T) is the set of inner vertices of T. The (D,f)-balance value of v with children v_1,...,v_k is computed as

bal_{D,f}(v)=D(fs(T_{v_1}),...,fs(T_{v_k}))

with D denoting the dissimilarity and fs denoting the f.size.
The f.size fs(T) of a tree T uses the function f, which maps any integer to a non-negative real number, to build a weighted sum of the out-degrees of all vertices in T. More precisely,

fs(T)=\sum_{v\in V(T)} f(deg+(v))

where V(T) is the set of all vertices of T and deg+(v) denotes the out-degree (i.e. the number of children) of the vertex v. The f-functions that are already implemented are f(x)=e^x and f(x)=ln(x+e).
The dissimilarity D(x_1,...,x_k) of a vector x_1,...,x_k assigns a non-negative value to the vector, is independent of the order of the vector entries and equals zero if and only if x_1=...=x_k. In this implementation the following dissimilarity functions are already built-in: mean deviation from the median (mdm), the sample variance (var) and the sample standard deviation (sd).
collesslikeI also allows the use of other functions for the weight function f and the dissimilarity D.

Special cases: For n=1 the function returns CL(T)=0 and a warning.

Usage

collesslikeI(tree, f.size, dissim)

Arguments

Value

collesslikeI returns the Colless-like index of the given tree according to the chosen function and dissimilarity.

Author(s)

Luise Kuehn, Sophie Kersting

References

A. Mir, L. Rotger, and F. Rosselló. Sound Colless-like balance indices for multifurcating trees. PLOSONE, 13(9):e0203401, 2018. doi: 10.1371/journal.pone.0203401

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
collesslikeI(tree, f.size="exp", dissim="mdm")
collesslikeI(tree, f.size="exp", dissim="var")
collesslikeI(tree, f.size="ln", dissim="sd")
myfsize <- function(x) return(x+1)
mydissim <- function(x) return (var(x))
collesslikeI(tree, f.size="myfsize",dissim = "mydissim")
collesslikeI(tree, f.size=function(x) x+1, dissim=stats::var)

Calculation of the equal weights Colless index for rooted binary trees

Description

This function calculates the equal weights Colless index I_2(T) for a given rooted binary tree T. I_2(T) is defined as

I_2(T)=\frac{1}{n-2}\cdot\sum_{u\in V_{in}(T), n_u>2} \frac{|n_{u_a}-n_{u_b}|}{n_u-2}

in which V_{in}(T) denotes the set of all inner vertices of T, and in which n_u, n_{u_a} and n_{u_b} denote the number of leaves in the pending subtrees that are rooted at u and the two direct descendants of u. The equal weights Colless index is an imbalance index.

For n=1 and n=2 the function returns I_2(T)=0 and a warning.

Usage

ewCollessI(tree)

Arguments

Value

ewCollessI returns the equal weights Colless index of the given tree.

Author(s)

Luise Kuehn

References

A. O. Mooers and S. B. Heard. Inferring Evolutionary Process from Phylogenetic Tree Shape. The Quarterly Review of Biology, 72(1), 1997. doi: 10.1086/419657.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
ewCollessI(tree)

Calculation of the Furnas rank for rooted binary trees

Description

This function calculates the Furnas rank F(T) for a given rooted binary tree T. F(T) is the unique rank of the tree T among all rooted binary trees with n leaves in the left-light rooted ordering. For details on the left-light rooted ordering as well as details on how the Furnas rank is computed, see "The generation of random, binary unordered trees" by G.W. Furnas (1984) or "Tree balance indices: a comprehensive survey" by Fischer et al. (2023). The Furnas rank is a balance index.

The concept of assigning each rooted binary tree a unique tuple (rank, n) allows to store many trees with minimal storage use.

The Furnas rank can be computed for trees with at most 2545 leaves. With type="double" the function stops for n\geq 49, since the ranks can then no longer be represented exactly as double.

Usage

furnasI(tree, type = "bigz")

Arguments

Value

furnasI returns the unique Furnas rank of the given tree, i.e. the rank of the tree among all rooted binary trees with n leaves in the left-light rooted ordering. Since the values can get quite large, the function returns them by default in big.z format (package gmp).

Author(s)

Luise Kuehn, Lina Herbst

References

G. W. Furnas. The generation of random, binary unordered trees. Journal of Classification, 1984. doi: 10.1007/bf01890123. URL https://doi.org/10.1007/bf01890123.

M. Kirkpatrick and M. Slatkin. Searching for evolutionary patterns in the shape of a phylogenetic tree. Evolution, 1993. doi: 10.1111/j.1558-5646.1993.tb02144.x.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
furnasI(tree)
furnasI(tree, type="double")

Calculation of rooted binary tree for tuple (rank, leaf number)

Description

This function calculates the unique tree T (in phylo format) for two given integer values r and n, with n denoting the number of leaves of T and r denoting the rank of T in the left-light rooted ordering of all rooted binary trees with n leaves. It is the inverse function of furnasI(). For details on how to calculate T (including algorithm) see "The generation of random, binary unordered trees" by G.W. Furnas (1984) or "Tree balance indices: a comprehensive survey" by Fischer et al. (2023).

furnasI_inv can be used e.g. to generate random rooted binary trees with a certain number of leaves. Also, the concept of assigning each rooted binary tree a unique tuple (rank, n) allows to store many trees with minimal storage use.

Usage

furnasI_inv(rank, n)

Arguments

Value

furnasI_inv returns the unique tree (in phylo format) for the given leaf number and rank.

Author(s)

Sophie Kersting

References

G. W. Furnas. The generation of random, binary unordered trees. Journal of Classification, 1984. doi: 10.1007/bf01890123. URL https://doi.org/10.1007/bf01890123.

Examples

furnasI_inv(rank=6,n=8)
furnasI_inv(rank="100000000000000000000",n=60)

Auxiliary functions

Description

getDescMatrix - Creates a matrix that contains the descendants of node i in row i.

getAncVec - Creates a vector that contains the parent (direct ancestor) of node i at position i.

getNodesOfDepth - Creates a matrix that contains the nodes of depth i in row i.

symBucketLexicoSort - Sorts the pairs of numbers lexicographically and returns ranking. Uses bucket sort.

getAllAncestors - Returns all ancestors of v including v itself.

cPL_inv - Returns the binary tree that belongs to the input label in an incomplete Newick format.

maxDepthLeaf - Returns the maximum depth of a leaf in the subtree that is rooted at v.

get.subtreesize - Creates a vector that contains at the i-th position the number of leaves in the pending subtree rooted at i.

getlca - Returns the name of the lowest common ancestor of the two input vertices v and w.

we_eth - Returns the Wedderburn-Etherington number we(n) for a given non-negative integer n\leq 2545. With type="double" the function stops for n\geq 49, since we(n) can then no longer be represented exactly as double.

getfurranks - Returns for each vertex i the Furnas rank of the subtree rooted at i (in bigz format, package gmp). The tree must have at most 2545 leaves.

getsubtree - Returns the pending subtree (in phylo format) that is rooted at the input vertex. If the input vertex is a leaf, the function returns the standard tree for n=1 (with 1 edge).

is_binary - Returns TRUE if the input tree is binary and FALSE otherwise.

is_phylo - Tests all requirements of the phylo format, and returns TRUE if the tree is correctly formatted, else FALSE with detailed feedback on the features that are not met.

tree_decomposition - Returns a list of length two, which contains the two pending subtrees that are rooted at the children of the root of the input tree. The smaller one (according to the number of leaves) is stated first.

tree_merge - Returns a rooted tree T in phylo format, which contains the input trees tree1 and tree2 as "left" and "right" maximal pending subtrees.

treenumber - Returns the unique tree number tn(T) of the given tree. tn(T) is the rank of the tree T among all rooted binary trees in the left-light rooted ordering. It can be calculated as follows:

tn(T)=F(T) + \sum_{i=1}^{n-1} we(i)

in which n is the number of leaves in T, F(T) is the Furnas rank of T, i.e. the rank of T in the left-light rooted ordering of all rooted binary trees with n leaves, and we(i) is the Wedderburn-Etherington number of i. The concept of assigning each rooted binary tree a unique tree number allows to store many trees with minimal storage use. For n=1 the function returns tn(T)=1 and a warning. With type="double" the function stops for n\geq 48, since the tree numbers can then no longer be represented exactly as double.

treenumber_inv - Returns the unique tree (in phylo format) for the given tree number.

auxE_l_X - Returns the sum of all products of l different values in X.

Usage

getDescMatrix(tree)

getAncVec(tree)

getNodesOfDepth(mat, root, n)

symBucketLexicoSort(workLabs)

getAllAncestors(tree, v)

cPL_inv(label)

maxDepthLeaf(tree, v = length(tree$tip.label) + 1)

get.subtreesize(tree)

getlca(tree, v, w)

we_eth(n, type = "bigz")

getfurranks(tree)

getsubtree(tree, subroot)

is_binary(tree)

is_phylo(tree)

tree_decomposition(tree)

tree_merge(tree1, tree2)

treenumber(tree, type = "bigz")

treenumber_inv(treenum)

auxE_l_X(subX, Xset)

Arguments

Value

desc_mat numeric matrix

anc_vec numeric vector

nodes_of_depth numeric matrix

ranking numeric vector

vectorWithAncs numeric vector

Author(s)

Sophie Kersting, Luise Kuehn and Lina Herbst

Examples

mat <- cbind(c(7,7,6,5,5,6),c(1,2,3,4,6,7))
tree <- list(edge=mat, tip.label=c("","","",""), Nnode=3)
getDescMatrix(tree)
mat <- cbind(c(5,5,5,5),c(1,2,3,4))
tree <- list(edge=mat, tip.label=c("","","",""), Nnode=1)
getDescMatrix(tree)
getAncVec(tree)
getNodesOfDepth(mat=getDescMatrix(tree),root=length(tree$tip.label)+1,
n=length(tree$tip.label))
myWorkLabs <- cbind(c(0,1,2,3,1,0),c(0,2,2,4,1,0))
symBucketLexicoSort(myWorkLabs)
getAllAncestors(tree,v=6)
cPL_inv(label=6)
maxDepthLeaf(tree,v=6)
get.subtreesize(tree)
getlca(tree,1,2)
we_eth(5)
we_eth(60)
we_eth(5, type="double")
getfurranks(tree)
getsubtree(tree,4)
is_binary(ape::read.tree(text="((((,),),(,)),(((,),),(,)));"))
is_phylo(ape::read.tree(text="((((,),),(,)),(((,),),(,)));"))
tree_decomposition(ape::read.tree(text="((((,),),(,)),(((,),),(,)));"))
treeA <- ape::read.tree(text="(((,),),(,));")
treeB <- ape::read.tree(text="((,),);")
tree_merge(treeA, treeB)
treenumber(ape::read.tree(text="((((,),),(,)),(((,),),(,)));"))
treenumber_inv(192)
treenumber_inv("5000000000000000000")
auxE_l_X(subX=3,Xset=c(1,1,2,2))

Calculation of the maximum width over maximum depth of the tree

Description

This function calculates the maximum width over maximum depth mWovermD(T) for a given rooted tree T. The tree must not necessarily be binary. For n>1, mWovermD(T) is defined as

mWovermD(T)=maxWidth(T) / h(T)

in which h(T) denotes the height of the tree T, which is the same as the maximum depth of any leaf in the tree, and maxWidth(T) denotes the maximum width of the tree T. The maximum width over maximum depth is a balance index.

Usage

mWovermD(tree)

Arguments

Value

mWovermD returns the maximum width over maximum depth of a tree.

Author(s)

Luise Kuehn

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
mWovermD(tree)
tree <- ape::read.tree(text="((,),((((,),),),(,)));")
mWovermD(tree)

Calculation of the (modified) maximum difference in widths for a rooted tree

Description

This function calculates the maximum difference in widths delW(T) and the modified maximum difference in width mdelW(T) for a given rooted tree T. The tree must not necessarily be binary. delW(T) is defined as

delW(T)=\max_{i=0,...,h(T)-1} |w(i+1)-w(i)|

and mdelW(T) is defined as

mdelW(T)=\max_{i=0,...,h(T)-1} w(i+1)-w(i)

in which h(T) denotes the height of the tree T and w(i) denotes the number of vertices in T that have depth i. The modified maximum difference in widths is a balance index, while the maximum difference in widths is not.

Note that earlier versions of this manual used the term 'maximum difference in widths' for what is the modified maximum difference in widths.

Usage

maxDelW(tree, method = "modified")

Arguments

Value

maxDelW returns the maximum difference in widths of a tree (if method is set to original) or the modified maximum difference in widths (if method is set to modified).

Author(s)

Sophie Kersting, Luise Kuehn

References

C. Colijn and J. Gardy. Phylogenetic tree shapes resolve disease transmission patterns. Evolution, Medicine, and Public Health, 2014(1):96-108, 2014. ISSN 2050-6201. doi: 10.1093/emph/eou018.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
maxDelW(tree, method="original")
tree <- ape::read.tree(text="((,),((((,),),),(,)));")
maxDelW(tree, method="modified")

Calculation of the maximum depth of the tree

Description

This function calculates the maximum depth of any vertex in a rooted tree T, which is at the same time its height h(T). The tree must not necessarily be binary. Formally, h(T) is defined as

h(T)=\max_{v\in V(T)} \delta(v)

with \delta(v) being the depth of the vertex v. The maximum depth is an imbalance index.

For n=1 the function returns h(T)=0 and a warning.

Usage

maxDepth(tree)

Arguments

Value

maxDepth returns the maximum depth, i.e. height, of a tree.

Author(s)

Luise Kuehn, Sophie Kersting

References

C. Colijn and J. Gardy. Phylogenetic tree shapes resolve disease transmission patterns. Evolution, Medicine, and Public Health, 2014(1):96-108, 2014. ISSN 2050-6201. doi: 10.1093/emph/eou018.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
maxDepth(tree)
tree <- ape::read.tree(text="((,),((((,),),),(,)));")
maxDepth(tree)

Calculation of the maximum width of the tree

Description

This function calculates the maximum width maxWidth(T) for a given rooted tree T. The tree must not necessarily be binary. maxWidth(T) is defined as

maxWidth(T)=\max_{i=0,...,h(T)} w(i)

in which h(T) denotes the height of the tree T and w(i) denotes the number of vertices in T that have depth i. The maximum width is a balance index.

Usage

maxWidth(tree)

Arguments

Value

maxWidth returns the maximum width of a tree.

Author(s)

Sophie Kersting

References

C. Colijn and J. Gardy. Phylogenetic tree shapes resolve disease transmission patterns. Evolution, Medicine, and Public Health, 2014(1):96-108, 2014. ISSN 2050-6201. doi: 10.1093/emph/eou018.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
maxWidth(tree)
tree <- ape::read.tree(text="((,),((((,),),),(,)));")
maxWidth(tree)

Calculation of the rooted quartet index for rooted trees

Description

This function calculates the rooted quartet index rQI(T) for a given rooted tree T. The tree must not necessarily be binary.

Let T be a rooted tree, whose leaves are 1,...,n. Let P_4 denote the set of all subsets of \{1,...,n\} that have cardinality 4. Let T(Q) denote the rooted quartet on Q\in P_4 that is obtained by taking the subgraph of T that is induced by Q and supressing its outdegree-1 vertices. T(Q) can have one of the five following shapes:

- Q_0^*: This is the caterpillar tree shape on 4 leaves, i.e. "(,(,(,)));" in Newick format. It has 2 automorphisms.
- Q_1^*: This is the tree shape on 4 leaves that has three pending subtrees rooted at the children of the root of T, one of them being a cherry and the other two being single vertices, i.e. "((,),,);" in Newick format. It has 4 automorphisms.
- Q_2^*: This is the tree shape on 4 leaves that has two pending subtrees rooted at the children of the root of T, one of them being a star tree shape on 3 leaves and the other one being a single vertex, i.e. "((,,),);" in Newick format. It has 6 automorphisms.
- Q_3^*: This is the fully balanced binary tree shape on 4 leaves, i.e. "((,),(,));" in Newick format. It has 8 automorphisms.
- Q_4^*: This is the star tree shape on 4 leaves, i.e. "(,,,);" in Newick format. It has 24 automorphisms.

T(Q) is assigned an rQI-value based on its shape, i.e. rQI(T(Q))=q_i if T(Q) has the shape Q_i^*. The values q_0,...,q_4 are chosen in such a way that they increase with the symmetry of the shape as measured by means of its number of automorphisms. Coronado et al. (2019) suggested the values q_0=0 and q_i=i or q_i=2^i for i=1,...,4.
The rooted quartet index rQI(T) of the tree T is then defined as the sum of the rQI-values of its rooted quartets:

rQI(T)=\sum_{Q\in P_4} rQI(T(Q))

The rooted quartet index is a balance index.

Usage

rQuartetI(tree, shapeVal = c(0, 1, 2, 3, 4))

Arguments

Value

rQuartetI returns the rooted quartet index of the given tree based on the chosen shape values (see description for details).

Author(s)

Sophie Kersting

References

T. M. Coronado, A. Mir, F. Rosselló, and G. Valiente. A balance index for phylogenetic trees based on rooted quartets. Journal of Mathematical Biology, 79(3):1105-1148, 2019. doi: 10.1007/s00285-019-01377-w. URL https://doi.org/10.1007/s00285-019-01377-w.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
rQuartetI(tree)

Calculation of the Rogers J index for rooted binary trees

Description

This function calculates the Rogers J index J(T) for a given rooted binary tree T. It is defined as the number of inner vertices whose balance value is unequal to zero, more precisely

J(T)=\sum_{u \in V_{in}(T)} (1-I(n_{u_a}=n_{u_b}))

in which V_{in}(T) denotes the set of all inner vertices of T, and in which n_{u_a} and n_{u_b} denote the number of leaves in the two pending subtrees that are rooted at the direct descendants of u.
Special cases: For n=1, the function returns J(T)=0 and a warning.

Usage

rogersI(tree)

Arguments

Value

rogersI returns the Rogers J index of the given tree.

Author(s)

Sophie Kersting

References

J. S. Rogers. Central Moments and Probability Distributions of Three Measures of Phylogenetic Tree Imbalance. Systematic Biology, 45(1):99-110, 1996. doi: 10.1093/sysbio/45.1.99.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
rogersI(tree)

Calculation of the s-shape statistic for rooted trees

Description

This function calculates the s-shape statistic sShape(T) for a given rooted tree T. The tree must not necessarily be binary, however sShape only fulfils the definition of an imbalance index on the space of binary trees. sShape(T) is defined as

sShape(T)=\sum_{u\in V_{in}(T)} log(n_u-1)

in which V_{in}(T) denotes the set of inner vertices of T and n_u denotes the number of leaves in the pending subtree that is rooted at u. An arbitrary logarithm base can be used (for binary trees it is common to use base 2).

For n=1 the function returns sShape(T)=0 and a warning.

Usage

sShapeI(tree, logbase = 2)

Arguments

Value

sShapeI returns the s-shape statistic of the given tree.

Author(s)

Luise Kuehn

References

M.G. Blum and O. Francois. Which random processes describe the tree of life? a large-scale study of phylogenetic tree imbalance. Systematic Biology, 2006.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
sShapeI(tree)

Calculation of the Sackin index for rooted trees

Description

This function calculates the Sackin index S(T) for a given rooted tree T. The tree must not necessarily be binary. S(T) is defined as

S(T)=\sum_{x\in V_L(T)} \delta(x)=\sum_{u\in V_{in}(T)} n_u

in which V_L(T) denotes the leaf set of T, \delta(x) denotes the depth of the leaf x, V_{in}(T) denotes the set of inner vertices in T, and n_u denotes the number of leaves in the pending subtree that is rooted at u. The Sackin index is an imbalance index.

For n=1 the function returns S(T)=0 and a warning.

Usage

sackinI(tree)

Arguments

Value

sackinI returns the Sackin index of the given tree.

Author(s)

Luise Kuehn

References

M.J. Sackin. "Good" and "Bad" Phenograms. Systematic Biology, 21(2):225-226, 1972. doi: 10.1093/sysbio/21.2.225.

K.-T. Shao and R.R. Sokal. Tree Balance. Systematic Zoology, 39(3):266, 1990. doi: 10.2307/2992186.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
sackinI(tree)

Calculation of the stairs1 value for rooted binary trees

Description

This function calculates the stairs1 value st1(T) for a given rooted binary tree T. It is a modified version of the Rogers J index and is defined as the fraction of inner vertices whose balance value is unequal to zero, more precisely

st1(T)=\frac{1}{n-1}\cdot\sum_{u \in V_{in}(T)} (1-I(n_{u_a}=n_{u_b}))

in which V_{in}(T) denotes the set of all inner vertices of T, and in which n_{u_a} and n_{u_b} denote the number of leaves in the two pending subtrees that are rooted at the direct descendants of u. The stairs1 value is an imbalance index.

Special cases: For n=1, the function returns st1(T)=0 and a warning.

Usage

stairs1(tree)

Arguments

Value

stairs1 returns the stairs1 value of the given tree.

Author(s)

Sophie Kersting

References

M. M. Norström, M. C. Prosperi, R. R. Gray, A. C. Karlsson, and M. Salemi. PhyloTempo: A Set of R Scripts for Assessing and Visualizing Temporal Clustering in Genealogies Inferred from Serially Sampled Viral Sequences. Evolutionary Bioinformatics, 8:EBO.S9738, 2012. ISSN 1176-9343, 1176-9343. doi:10.4137/EBO.S9738.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
stairs1(tree)

Calculation of the stairs2 value for rooted binary trees

Description

This function calculates the stairs2 value st2(T) for a given rooted binary tree T. It is defined as the mean ratio between the leaf numbers of the smaller and larger pending subtree over all inner vertices, more precisely

st2(T)=\frac{1}{n-1}\cdot\sum_{u \in V_{in}(T)} \frac{n_{u_a}}{n_{u_b}}

in which V_{in}(T) denotes the set of all inner vertices of T, and in which n_{u_a}\geq n_{u_b} denote the number of leaves in the two pending subtrees that are rooted at the direct descendants of u. The stairs2 value is an imbalance index.

Special cases: For n=1, the function returns st2(T)=0 and a warning.

Usage

stairs2(tree)

Arguments

Value

stairs2 returns the stairs2 value of the given tree.

Author(s)

Sophie Kersting

References

C. Colijn and J. Gardy. Phylogenetic tree shapes resolve disease transmission patterns. Evolution, Medicine, and Public Health, 2014(1):96-108, 2014. ISSN 2050-6201. doi: 10.1093/emph/eou018.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
stairs2(tree)

Calculation of the symmetry nodes index for rooted binary trees

Description

This function calculates the symmetry nodes index SNI(T) for a given rooted binary tree T. SNI(T) is defined as the number of inner vertices v that are not symmetry nodes, i.e. the two pending subtrees rooted at the children of v do not have the same tree shape.

For n=1 the function returns SNI(T)=0 and a warning.

Usage

symNodesI(tree)

Arguments

Value

symNodesI returns the symmetry nodes index of the given tree.

Author(s)

Sophie Kersting

References

S. J. Kersting and M. Fischer. Measuring tree balance using symmetry nodes — A new balance index and its extremal properties. Mathematical Biosciences, page 108690, 2021. ISSN 0025-5564. doi:https://doi.org/10.1016/j.mbs.2021.108690

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
symNodesI(tree)

Calculation of the total cophenetic index for rooted trees

Description

This function calculates the total cophenetic index TCI(T) of a given rooted tree T. The tree must not necessarily be binary. TCI(T) is defined as

TCI(T)=\sum_{1\leq i<j\leq n} \delta(lca(i,j))=\sum_{u\in V_{in}(T)\setminus\{\rho\}} binom(n_u,2)

in which \delta(lca(i,j)) denotes the depth of the lowest common ancestor of the two leaves i and j and V_{in}(T)\setminus\{\rho\} denotes the set of all inner vertices exept the root and n_u denotes the number of descendant leaves of u. The second formula is useful for efficient computation of TCI(T). The total cophenetic index is an imbalance index.

For n=1 the function returns TCI(T)=0.

Usage

totCophI(tree)

Arguments

Value

totCophI returns the total cophenetic index of the given tree.

Author(s)

Sophie Kersting

References

A. Mir, F. Rosselló, and L. Rotger. A new balance index for phylogenetic trees. Mathematical Bio-sciences, 241(1):125-136, 2013. doi: 10.1016/j.mbs.2012.10.005.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
totCophI(tree)
tree <- ape::read.tree(text="((,),((((,),),),(,)));")
totCophI(tree)
tree <- ape::read.tree(text="((,,,),(,,));")
totCophI(tree)

Calculation of the total internal path length for rooted trees

Description

This function calculates the total internal path length TIP(T) for a given rooted tree T. The tree must not necessarily be binary. TIP(T) is defined as

TIP(T)=\sum_{x\in V_{in}(T)} \delta(x)

in which V_{in}(T) denotes the set of inner vertices of T, and \delta(x) denotes the depth of the vertex x. The total internal path length is an imbalance index.

Usage

totIntPathLen(tree)

Arguments

Value

totIntPathLen returns the total internal path length of the given tree.

Author(s)

Luise Kuehn

References

D. E. Knuth. The art of computer programming: fundamental algorithms, volume 1. Addison-Wesley, Reading, Mass, 3rd edition, 1997. ISBN 9780201896831.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,,),),(,)));")
totIntPathLen(tree)

Calculation of the total path length for rooted trees

Description

This function calculates the total path length TPL(T) for a given rooted tree T. The tree must not necessarily be binary. TPL(T) is defined as

TPL(T)=\sum_{x\in V(T)} \delta(x)

in which V(T) denotes the set of vertices of T, and \delta(x) denotes the depth of the vertex x. The total path length is an imbalance index.

For n=1 the function returns TPL(T)=0 and a warning.

Usage

totPathLen(tree)

Arguments

Value

totPathLen returns the total path length of the given tree.

Author(s)

Luise Kuehn

References

TODO

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,,),),(,)));")
totPathLen(tree)

Calculation of the variance of leaf depths index for rooted trees

Description

This function calculates the variance of leaf depths index VLD(T) for a given rooted tree T. The tree must not necessarily be binary. VLD(T) is defined as

VLD(T)=\frac{1}{n}\cdot\sum_{x\in V_L(T)} (\delta(x)-N(T))^2

in which n denotes the number of leaves of T, V_L(T) denotes the set of leaves of T, \delta(x) denotes the depth of the leaf x and N(T) denotes the average leaf depth of T.

For n=1 the function returns VLD(T)=0 and a warning.

Usage

varLeafDepI(tree)

Arguments

Value

varLeafDepI returns the variance of leaf depths index of the given tree.

Author(s)

Sophie Kersting

References

T. M. Coronado, A. Mir, F. Rosselló, and L. Rotger. On Sackin's original proposal: the variance of the leaves' depths as a phylogenetic balance index. BMC Bioinformatics, 21(1), 2020. doi: 10.1186/s12859-020-3405-1. URL https://doi.org/10.1186/s12859-020-3405-1.

M. J. Sackin. "Good" and "Bad" Phenograms. Systematic Biology, 21(2):225-226, 1972. doi: 10.1093/sysbio/21.2.225.

K.-T. Shao and R. R. Sokal. Tree Balance. Systematic Zoology, 39(3):266, 1990. doi: 10.2307/2992186.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
varLeafDepI(tree)

Wedderburn Etherington numbers (from OEIS)

Description

Contains a vector of Wedderburn Etherington numbers for n=1 to n=2545. Since these numbers grow very quickly, they are stored exactly as big integers (bigz format, package gmp). Single values can also be accessed with we_eth(n), which optionally returns them as double (only for n\leq 48).

Usage

data(wedEth)

Format

bigz vector (package gmp) of length 2545

Source

OEIS Sequence A001190 available at https://oeis.org/A001190

Examples

data(wedEth)
wedEth[5]
wedEth[50]

Calculation of weighted l1 distance index for rooted binary trees

Description

This function calculates the weighted l1 distance index D_{l1}(T) for a given rooted binary tree T. D_{l1}(T) is defined as

D_{l1}(T)=\sum_{z=2}^n z \cdot |f_n(z)-p_n(z)|

in which n denotes the number of leaves of T, f_n(z) denotes the frequency of pending subtrees of size z in T and p_n(z) is the expected number of pending subtrees of size z under the Yule model, i.e. p_n(z)=\frac{1}{n-1} if z=n and otherwise \frac{n}{n-1}\cdot\frac{2}{z\cdot(z+1)}.

For n=1 the function returns D_{l1}(T)=0.

Usage

weighL1dist(tree)

Arguments

Value

weighL1distI returns the weighted l1 distance index of the given tree.

Author(s)

Sophie Kersting

References

M. G. Blum and O. François. On statistical tests of phylogenetic tree imbalance: The Sackin and other indices revisited. Mathematical Biosciences, 195(2):141-153, 2005. doi: 10.1016/j.mbs.2005.03.003.

Examples

tree <- ape::read.tree(text="((((,),),(,)),(((,),),(,)));")
weighL1dist(tree)