decostand: Standardizaton Methods for Community Ecology
Description
The function provides some popular (and effective) standardization
methods for community ecologists.
Usage
decostand(x, method, MARGIN=NULL)
wisconsin(x)
Arguments
x
Community data matrix.
method
Standardization method.
MARGIN
Margin, if default is not acceptable.
Value
Returns the standardized matrix.
Details
The function offers following standardization methods for community
data:
total: divide by margin total (default margin 1).
max: divide by margin maximum (default margin 2).
freq: divide by margin maximum and multiply by number of
non-zero items, so that the average of non-zero entries is one (default
margin 2).
normalize: make margin sum of squares equal to unity (default
margin 1).
range: standardize values into range 0...1 (default
margin 2).
standardize: scale into zero mean and unit variance
(default margin 2).
pa: scale into presence/absence scale (0/1).
Standardization, as contrasted to transformation, means that the
entries are transformed relative to other entries.
All methods have a default margin. Margin 1 means rows (sites
in a
normal data set) and margin 2 means columns (species in a normal
data set).
Command wisconsin is a shortcut to common Wisconsin double
standardization where species (margin 2) are first standardized
by maxima (max) and then sites (margin 1) by
site totals (tot).