If a tree is available in a text-based format, it should not be too difficult to load into R.
A straightforward, if cumbersome, way to enter trees into R is by manual text entry:
Beware common gotchas when entering text:
Ensure that the tree string ends in a semi-colon.
Look out for ((double brackets)) or brackets enclosing a single node: the resultant ‘invisible nodes’ can cause R to crash.
badTree <- ape::read.tree(text='((A, B), (((C, D), ((E), F))));') plot(badTree) ape::nodelabels(bg = c(3, 3, 2, 2, 3, 3, 2))
The text is expected in Newick format, so can contain edge lengths - but edge lengths must be included for every edge of the tree, or they will be ignored.
First off, make sure that you are comfortable telling R where to find a file.
You can load trees from a nexus file using:
filename <- "my_file_name.nex" ape::read.nexus(filename)
If the file contains multiple trees, this will return a list of all trees in the file, with the class
multiPhylo. If there is a single tree, then this will be returned as a tree of class
phylo unless the option
force.multiPhylo = TRUE. This can be useful when an unknown number of trees are to be processed in bulk, for example by
Newick trees can be read with
phytools::read.newick(filename) does not report an error when a ‘node’ has a single descendant (which will often denote a misspecified tree).
Trees should be saved in parenthetical format (TNT command
tsav*), rather than TNT’s compressed format (TNT command
The TNT command
taxname= will write taxon names to file, which results in larger but easier to read files. Trees in such a file will be read using the terminal names saved within the file. The TNT command
taxname- saves just the numbers of the terminals. In order for the trees to be reunited with the names of their tips, terminal labels will be read from the linked matrix file listed in the first line of the .tre file. Ensure that this file exists in the expected location. If it does not, use
ReadTntTree(treeFile, relativePath = '../path/to/tipNameFile'), or
tipLabels to manually specify the names of the tips (e.g.
ReadTntTree(treeFile, tipLabels = c('outgroup', letters[1:8])).
Are there other formats that should be listed here? Please let me know by opening an issue.
To save a tree to a text file, use
ape::write.tree(tree, file='filename.txt') for Newick format (widely supported by most phylogenetic software), or
ape::write.nexus(tree, file='filename.nex') for Nexus format.