compute.brlen {ape} | R Documentation

## Branch Lengths Computation

### Description

This function computes branch lengths of a tree using different methods.

### Usage

    compute.brlen(phy, method = "Grafen", power = 1, ...)

### Arguments

`phy` | an object of class `phylo` representing the tree.
`method` | the method to be used to compute the branch lengths; this must be one of the followings: (i) `"Grafen"` (the default), (ii) a numeric vector, or (iii) a function.
`power` | The power at which heights must be raised (see below).
`...` | further argument(s) to be passed to `method` if it is a function.

### Details

Grafen's (1989) computation of branch lengths: each node is given a ‘height’, namely the number of leaves of the subtree minus one, 0 for leaves. Each height is scaled so that root height is 1, and then raised at power 'rho' (> 0). Branch lengths are then computed as the difference between height of lower node and height of upper node.

If one or several numeric values are provided as `method`, they are recycled if necessary. If a function is given instead, further arguments are given in place of `...` (they must be named, see examples).

Zero-length branches are not treated as multichotomies, and thus may need to be collapsed (see `di2multi`).

### Value

An object of class `phylo` with branch lengths.

### Author(s)

Julien Dutheil julien.dutheil@univ-montp2.fr and Emmanuel Paradis

### References

Grafen, A. (1989) The phylogenetic regression. Philosophical Transactions of the Royal society of London. Series B. Biological Sciences, 326, 119–157.

### See Also

`read.tree` for a description of `phylo` objects, `di2multi`, `multi2di`

### Examples

    data(bird.orders)
    plot(compute.brlen(bird.orders, 1))
    plot(compute.brlen(bird.orders, runif, min = 0, max = 5))
    layout(matrix(1:4, 2, 2))
    plot(compute.brlen(bird.orders, power=1), main=expression(rho==1))
    plot(compute.brlen(bird.orders, power=3), main=expression(rho==3))
    plot(compute.brlen(bird.orders, power=0.5), main=expression(rho==0.5))
    plot(compute.brlen(bird.orders, power=0.1), main=expression(rho==0.1))
    layout(1)

[Package ape version 5.0 Index]