mjn: Median-Joining Network

In pegas: Population and Evolutionary Genetics Analysis System

Median-Joining Network

Description

This function computes the median-joining network (MJN) as described by Bandelt et al. (1999).

Usage

mjn(x, epsilon = 0, max.n.cost = 10000, prefix = "median.vector_",
    quiet = FALSE)
## S3 method for class 'mjn'
plot(x, shape = c("circles", "diamonds"),
      bg = c("green", "slategrey"), labels = FALSE, ...)

Arguments

x	a matrix (or data frame) of DNA sequences or binary 0/1 data; an object of class "mjn" for plot.
epsilon	tolerance parameter.
max.n.cost	the maximum number of costs to be computed.
prefix	the prefix used to label the median vectors.
quiet	a logical value; by default, the progress of the calculatins is printed.
shape, bg	the default shapes and colours for observed haplotypes and median vectors.
labels	by default, the labels of the haplotypes are printed.
...	other arguments passed to plot.haploNet.

Details

MJN is a network method where unobserved sequences (the median vectors) are reconstructed and included in the final network. Unlike mst, rmst, and msn, mjn works with the original sequences, the distances being calculated internally using a Hamming distance method (with dist(x, "manhattan") for binary data or dist.dna(x, "N") for DNA sequences).

The parameter epsilon controls how the search for new median vectors is performed: the larger this parameter, the wider the search (see the example with binary data).

If the sequences are very divergent, the search for new median vectors can take a very long time. The argument max.n.cost controls how many such vectors are added to the network (the default value should avoid the function to run endlessly).

The arguments shape and bg must be of length two (unlike in plot.haploNet). It is possible to have more flexibility when plotting the MJN by changing its class, for instance with the output in the examples below: class(nt0) <- "haplotNet".

Value

an object of class c("mjn", "haploNet") with an extra attribute (data) containing the original data together with the median vectors.

Note

Since pegas 1.0, mjn is expected to run in reasonable times (less than 15 sec with 100 sequences). Bandelt et al. (1999) reported long computing times because of the need to compute a lot of median vectors. Running times also depend on the level of polymorphism in the data (see above).

Author(s)

Emmanuel Paradis

References

Bandelt, H. J., Forster, P. and Rohl, A. (1999) Median-joining networks for inferring intraspecific phylogenies. Molecular Biology and Evolution, 16, 37–48.

See Also

haploNet, mst

Examples

## data in Table 1 of Bandelt et al. (1999):
x <- c(0, 0, 0, 0, 0, 0, 0, 0, 0,
       1, 1, 1, 1, 0, 0, 0, 0, 0,
       1, 0, 0, 0, 1, 1, 1, 0, 0,
       0, 1, 1, 1, 1, 1, 0, 1, 1)
x <- matrix(x, 4, 9, byrow = TRUE)
rownames(x) <- LETTERS[1:4]
(nt0 <- mjn(x))
(nt1 <- mjn(x, 1))
(nt2 <- mjn(x, 2))
plot(nt0)

## Not run: 
## same like in Fig. 4 of Bandelt et al. (1999):
plotNetMDS(nt2, dist(attr(nt2, "data"), "manhattan"), 3)

## End(Not run)

## data in Table 2 of Bandelt et al. (1999):
z <- list(c("g", "a", "a", "a", "a", "a", "a", "a", "a", "a", "a", "a"),
          c("a", "g", "g", "a", "a", "a", "a", "a", "a", "a", "a", "a"),
          c("a", "a", "a", "g", "a", "a", "a", "a", "a", "a", "g", "g"),
          c("a", "a", "a", "a", "g", "g", "a", "a", "a", "a", "g", "g"),
          c("a", "a", "a", "a", "a", "a", "a", "a", "g", "g", "c", "c"),
          c("a", "a", "a", "a", "a", "a", "g", "g", "g", "g", "a", "a"))
names(z) <- c("A1", "A2", "B1", "B2", "C", "D")
z <- as.matrix(as.DNAbin(z))
(ntz <- mjn(z, 2))

## Not run: 
## same like in Fig. 5 of Bandelt et al. (1999):
plotNetMDS(ntz, dist.dna(attr(ntz, "data"), "N"), 3)

## End(Not run)

pegas documentation built on May 29, 2024, 2:27 a.m.