prabclus (version 2.1-3)

prabinit: Presence-absence/abundance matrix initialization

Description

prabinit converts a matrix into an object of class prab (presence-absence). The matrix may be read from a file or an R-object. It may be a 0-1 matrix or a matrix with non-negative entries (usually abundances) from which a 0-1 matrix can be generated. print.prab is a print method for such objects.

Usage

prabinit(file = NULL, prabmatrix = NULL, rows.are.species = TRUE,
neighborhood = "none", geodist=NULL, gtf=0.1,
distance = "kulczynski", toprab = FALSE, toprabp
= 0.05, outc = 5.2)
## S3 method for class 'prab':
print(x, ...)

Arguments

file

string. nen-negative matrix ASCII file (such as example dataset kykladspecreg.dat) from which the matrix is read by read.table. The usual interpretation is that it is a species-by-regions matrix of species presences/a

prabmatrix

matrix with non-negative entries. Either file or prabmatrix should be NA.

rows.are.species

logical. If TRUE, rows are interpreted as species and columns are interpreted as regions. In this case, rows and columns are interchanged by prabinit.

neighborhood

A string or a list with a component for every region. The components are vectors of integers indicating neighboring regions. A region without neighbors (e.g., an island) should be assigned a vector numeric(0). If neighbo

geodist

matrix of non-negative reals. Geographical distances between regions. Only used if distance="geco".

gtf

tuning constant for geco-distance if distance="geco", see geco.

distance

"kulczynski", "jaccard", "geco", "qkulczynski", "logkulczynski" (this calls function qkulczynski with log.distance=TRUE), or "none". The di

toprab

logical. If TRUE, a presence-absence matrix is computed from the non-negative input matrix. "Absence", i.e., the entry 0, is chosen if the original entry is 0, or the original entry is both smaller than toprabp times

toprabp

numerical between 0 and 1, see toprab.

outc

numerical. Tuning constant for the outlier identification associated with toprab=TRUE. An entry smaller than outc*mad times the median is considered as a lower outlier.

x

object of class prab.

...

necessary for print method.

Value

• An object of class prab, which is a list with components
• distmat
  distance matrix between species.
• prab
  presence-absence or abundance matrix. Rows are regions, columns are species.
• nb
  neighborhood list, see above.
• regperspec
  vector of the number of regions occupied by a species.
• specperreg
  vector of the number of species present in a region.
• n.species
  number of species (in the prab-object, see nonzero).
• n.regions
  number of regions.
• distance
  string denoting the chosen distance measure.
• geodist
  non-negative matrix. see above.
• gtf
  numeric. see above.
• spatial
  TRUE, if there is a specified neighborhood structure.
• nonzero
  logical vector. The length is the number of species in the original file/matrix. If FALSE, the corresponding species had only zero entries and was therefore absent. Note that these species are not included in any other component of a prab object, i.e., n.species is the number of TRUE-entries in nonzero.

Details

Species that are absent in all regions are omitted.

See Also

read.table, jaccard, kulczynski, geco, qkulczynski, nbtest

Examples

# If you want to use your own ASCII data files, use
# x <- prabinit(file="path/prabmatrixfile",
# neighborhood="path/neighborhoodfile")
data(kykladspecreg)
data(nb)
prabinit(prabmatrix=kykladspecreg, neighborhood=nb)