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Create phytree object


Tree = phytree(B)
Tree = phytree(B, D)
Tree = phytree(B, C)
Tree = phytree(BC)
Tree = phytree(..., N)
Tree = phytree



Numeric array of size [NUMBRANCHES X 2] in which every row represents a branch of the tree. It contains two pointers to the branch or leaf nodes, which are its children.

CColumn vector with distances for every branch.
DColumn vector with distances from every node to their parent branch.
BCCombined matrix with pointers to branches or leaves, and distances of branches.


Cell array with the names of leaves and branches.


Tree = phytree(B) creates an ultrametric phylogenetic tree object. In an ultrametric phylogenetic tree object, all leaves are the same distance from the root.

B is a numeric array of size [NUMBRANCHES X 2] in which every row represents a branch of the tree and it contains two pointers to the branch or leaf nodes, which are its children.

Leaf nodes are numbered from 1 to NUMLEAVES and branch nodes are numbered from NUMLEAVES + 1 to NUMLEAVES + NUMBRANCHES. Note that because only binary trees are allowed, NUMLEAVES = NUMBRANCHES + 1.

Branches are defined in chronological order (for example, B(i,:) > NUMLEAVES + i). As a consequence, the first row can only have pointers to leaves, and the last row must represent the root branch. Parent-child distances are set to 1, unless the child is a leaf and to satisfy the ultrametric condition of the tree its distance is increased.

Given a tree with three leaves and two branches as an example.

In the MATLAB® Command Window, type

B = [1 2 ; 3 4]

 B =

     1     2
     3     4

tree = phytree(B)

 Phylogenetic tree object with 3 leaves (2 branches)


Tree = phytree(B, D) creates an additive (ultrametric or nonultrametric) phylogenetic tree object with branch distances defined by D. D is a numeric array of size [NUMNODES X 1] with the distances of every child node (leaf or branch) to its parent branch equal to NUMNODES = NUMLEAVES + NUMBRANCHES. The last distance in D is the distance of the root node and is meaningless.

b = [1 2 ; 3 4 ]

b =

     1     2
     3     4

d = [1; 2; 1.5; 1; 0]

d =



Tree = phytree(B, C) creates an ultrametric phylogenetic tree object with distances between branches and leaves defined by C. C is a numeric array of size [NUMBRANCHES X 1], which contains the distance from each branch to the leaves. In ultrametric trees, all of the leaves are at the same location (same distance to the root).

b = [1 2 ; 3 4]

b =

     1     2
     3     4

c = [1 4]'

c =



Tree = phytree(BC) creates an ultrametric phylogenetic binary tree object with branch pointers in BC(:,[1 2]) and branch coordinates in BC(:,3). Same as phytree(B,C).

Tree = phytree(..., N) specifies the names for the leaves and/or the branches. N is a cell of strings. If NUMEL(N)==NUMLEAVES, then the names are assigned chronologically to the leaves. If NUMEL(N)==NUMBRANCHES, the names are assigned to the branch nodes. If NUMEL(N)==NUMLEAVES + NUMBRANCHES, all the nodes are named. Unassigned names default to 'Leaf #' and/or 'Branch #' as required.

Tree = phytree creates an empty phylogenetic tree object.


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Create a Phylogenetic Tree

This example shows how to create a phylogenetic tree from a multiple sequence alignment file.

Read a multiple sequence alignment file.

Sequences = multialignread('aagag.aln');

Calculate the distance between each pair of sequences.

distances = seqpdist(Sequences);

Construct a phylogenetic tree object from the pairwise distances calculated previously.

tree = seqlinkage(distances);

View the phylogenetic tree.


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