SI.stats {RGeostats}

R Documentation

Calculate Spatial Indices

Description

Calculate Spatial Indices

Usage

SI.stats(db, flag.plot=FALSE)

Arguments

db	Name of the db-class which contains the data (and the weight)
flag.plot	When TRUE, a curve is plotted. See Details for more...

Details

The spreading area 'sparea' (expressed in square nautical miles) is derived from the curve expressing (Q-Q(T))/Q as a function of T. T being the cumulated area occupied by the density values, ranked in decreasing order. Q(T) the corresponding cumulated abundance and Q the overall abundance. The spreading area is simply defined as twice the area below this curve.

Value

A list which contains the following:

• total abundance

• positive area

• equivalent area

• spreading index

• the elements of the graphics (T, QT)

References

Woillez, M., Poulard, J-C., Rivoirard, J., Petitgas, P., and Bez, N. 2007. Indices for capturing spatial patterns and their evolution in time, with application to European hake (Merluccius merluccius) in the Bay of Biscay. - ICES Journal of Marine Science, 64: 537-550. http://icesjms.oxfordjournals.org/content/64/3/537.abstract

Woillez, M., Rivoirard, J., and Petitgas, P. 2009. Notes on survey-based spatial indicators for monitoring fish populations. - Aquatic Living Resources, 22: 155-164. http://journals.cambridge.org/action/displayAbstract?fromPage=online&aid=8215490

Examples

# Load data
rg.load(filename="Demo.hake.bob.db.data",objname="db.data")
rg.load(filename="Demo.hake.bob.poly.data",objname="poly.data")
projec.define(projection="mean",db=db.data)

# Abundance index, Positive area, Equivalent area and Spreading area
SI.stats(db.data,flag.plot=TRUE)

rm(db.data,poly.data)

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