[R] problem accessing trees after read.nexus from ape package

[Ben Bolker]

Betty Gilbert <lgilbert <at> berkeley.edu> writes:

> 
> Hello,
> I've been trying to figure out how to access the individual elements 
> from an object of class phylo.
> I am reading in 201 trees created by paup as below.
> 
> >  read.nexus("A_30knj_200t.txt", tree.names= NULL) -> anj30

[snip]
> 
>   x<- anj30[1]
> >  class(x)
> [1] "list"
> 
> >  as.phylo(x)
> Error in as.phylo(x) : no applicable method for "as.phylo"
> >  cophenetic.phylo(x)
> Error in cophenetic.phylo(x) : your tree has no branch lengths defined
> 
> and
> >  cophenetic.phylo(anj30[1])
> Error in cophenetic.phylo(anj30[1]) : your tree has no branch lengths defined
> 

  (1) using [[ instead of [ will help; [ returns a LIST (possibly just
a one-element list), while [[ returns an ELEMENT of the list.

  e.g.:

> x <- list("a","b","c")
> x[1]
[[1]]
[1] "a"

> class(x[1])
[1] "list"
> x[[1]]
[1] "a"
> class(x[[1]])
[1] "character"


  (2) cophy <- lapply(anj30,cophenetic.phylo) should process all
of your phylogenies and return the answer as a list of cophylogenies.

  good luck,
    Ben Bolker