## which.edge.R (2009-05-10)
## Identifies Edges of a Tree
## Copyright 2004-2009 Emmanuel Paradis
## This file is part of the R-package `ape'.
## See the file ../COPYING for licensing issues.
getMRCA <- function(phy, tip)
### Find the MRCA of the tips given as `tip'
### (see `root.R' for comments on the code)
{
Ntip <- length(phy$tip.label)
seq.nod <- .Call("seq_root2tip", phy$edge, Ntip,
phy$Nnode, PACKAGE = "ape")
sn <- seq.nod[tip]
MRCA <- Ntip + 1
i <- 2
repeat {
x <- unique(unlist(lapply(sn, "[", i)))
if (length(x) != 1) break
MRCA <- x
i <- i + 1
}
MRCA
}
which.edge <- function(phy, group)
{
if (!inherits(phy, "phylo"))
stop('object "phy" is not of class "phylo"')
if (is.character(group))
group <- which(phy$tip.label %in% group)
if (length(group) == 1)
return(match(group, phy$edge[, 2]))
nb.tip <- length(phy$tip.label)
MRCA <- getMRCA(phy, group)
if (MRCA == nb.tip + 1) {
from <- 1
to <- dim(phy$edge)[1]
} else {
from <- which(phy$edge[, 2] == MRCA) + 1
to <- max(which(phy$edge[, 2] %in% group))
}
wh <- from:to
tmp <- phy$edge[wh, 2]
## check that there are no extra tips:
## (we do this by selecting the tips in `group' and the nodes
## i.e., the internal edges)
test <- tmp %in% group | tmp > nb.tip
if (any(!test)) {
wh <- wh[test] # drop the extra tips
## see if there are no extra internal edges:
tmp <- phy$edge[wh, ]
test <- !(tmp[, 2] %in% tmp[, 1]) & tmp[, 2] > nb.tip
while (any(test)){
wh <- wh[!test]
tmp <- phy$edge[wh, ]
test <- !(tmp[, 2] %in% tmp[, 1]) & tmp[, 2] > nb.tip
}
}
wh
}
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