+-------------+-------------------+
| possumDiv   | R Documentation   |
+-------------+-------------------+

Possum Diversity Data
---------------------

Description
~~~~~~~~~~~

Possum diversity data: As issued from a study of the diversity of possum
(arboreal marsupials) in the Montane ash forest (Australia), this
dataset was collected in view of the management of hardwood forest to
take conservation and recreation values, as well as wood production,
into account.

The study is fully described in the two references. The number of
different species of arboreal marsupials (possum) was observed on 151
different 3ha sites with uniform vegetation. For each site the nine
variable measures (see below) were recorded. The problem is to model the
relationship between ``diversity`` and these other variables.

Usage
~~~~~

::

    data(possumDiv)

Format
~~~~~~

Two different representations of the same data are available:

``possumDiv`` is a data frame of 151 observations of 9 variables, where
the last two are factors, ``eucalyptus`` with 3 levels and ``aspect``
with 4 levels.

``possum.mat`` is a numeric (integer) matrix of 151 rows (observations)
and 14 columns (variables) where the last seven ones are 0-1 dummy
variables, three (``E.*``) are coding for the kind of ``eucalyptus`` and
the last four are 0-1 coding for the ``aspect`` factor.

The variables have the following meaning:

Diversity
    main variable of interest is the number of different species of
    arboreal marsupial (possum) observed, with values in 0:5.

Shrubs
    the number of shrubs.

Stumps
    the number of cut stumps from past logging operations.

Stags
    the number of stags (hollow-bearing trees).

Bark
    bark index (integer) vector reflecting the quantity of decorticating
    bark.

Habitat
    an integer score indicating the suitability of nesting and foraging
    habitat for Leadbeater's possum.

BAcacia
    a numeric vector giving the basal area of acacia species.

eucalyptus
    a 3-level ``factor`` specifying the species of eucalypt with the
    greatest stand basal area. This has the same information as the
    following three variables

E.regnans
    0-1 indicator for Eucalyptus regnans

E.delegatensis
    0-1 indicator for Eucalyptus deleg.

E.nitens
    0-1 indicator for Eucalyptus nitens

aspect
    a 4-level ``factor`` specifying the aspect of the site. It is the
    same information as the following four variables.

NW-NE
    0-1 indicator

NW-SE
    0-1 indicator

SE-SW
    0-1 indicator

SW-NW
    0-1 indicator

Source
~~~~~~

Eva Cantoni (2004) Analysis of Robust Quasi-deviances for Generalized
Linear Models. *Journal of Statistical Software* **10**, 04,
`http://www.jstatsoft.org/v10/i04 <http://www.jstatsoft.org/v10/i04>`_

References
~~~~~~~~~~

Lindenmayer, D. B., Cunningham, R. B., Tanton, M. T., Nix, H. A. and
Smith, A. P. (1991) The conservation of arboreal marsupials in the
montane ash forests of the central highlands of victoria, south-east
australia: III. The habitat requirements of leadbeater's possum
*gymnobelideus leadbeateri* and models of the diversity and abundance of
arboreal marsupials. *Biological Conservation* **56**, 295–315.

Lindenmayer, D. B., Cunningham, R. B., Tanton, M. T., Smith, A. P. and
Nix, H. A. (1990) The conservation of arboreal marsupials in the montane
ash forests of the victoria, south-east australia, I. Factors
influencing the occupancy of trees with hollows, *Biological
Conservation* **54**, 111–131.

See also the references in ``glmrob``.

Examples
~~~~~~~~

::

    data(possumDiv)
    head(possum.mat)

    str(possumDiv)
    ## summarize all variables as multilevel factors:
    summary(as.data.frame(lapply(possumDiv, function(v)
                                 if(is.integer(v)) factor(v) else v)))

