## howmanytrees.R (2004-12-23)
## Calculate Numbers of Phylogenetic Trees
## Copyright 2004 Emmanuel Paradis
## This file is part of the R-package `ape'.
## See the file ../COPYING for licensing issues.
howmanytrees <- function(n, rooted = TRUE, binary = TRUE,
labeled = TRUE, detail = FALSE)
{
if (!labeled && !(rooted & binary))
stop("can compute number of unlabeled trees only for rooted binary cases.")
if (n < 3) N <- 1 else {
if (labeled) {
if (!rooted) n <- n - 1
if (binary) N <- prod(seq(1, (2*n - 3), by = 2))
else {
N <- matrix(0, n, n - 1)
N[1:n, 1] <- 1
for (i in 3:n)
for (j in 2:(i - 1))
N[i, j] <- (i + j - 2)*N[i - 1, j - 1] + j*N[i - 1, j]
if (detail) {
rownames(N) <- 1:n
colnames(N) <- 1:(n - 1)
} else N <- sum(N[n, ])
}
} else {
N <- numeric(n)
N[1] <- 1
for (i in 2:n)
if (i %% 2) N[i] <- sum(N[1:((i - 1)/2)]*N[(i - 1):((i + 1)/2)]) else {
x <- N[1:(i/2)]
y <- N[(i - 1):(i/2)]
y[length(y)] <- (y[length(y)] + 1)/2
N[i] <- sum(x*y)
}
if (detail) names(N) <- 1:n else N <- N[n]
}
}
N
}
Add the following code to your website.
For more information on customizing the embed code, read Embedding Snippets.