SI.patches {RGeostats}

R Documentation

Number of spatial patches

Description

Identify and count the spatial patches.

Usage

SI.patches(db, D.min = 100, A.min = 10,...)

Arguments

db	Name of the db-class which contains the data
D.min	Select minimum distance from sample to patch centre to identify patches (units are those of coordinates)
A.min	Visualisation of gravity centres for those patches with abundance > A.min (in
...	Additional graphic parameters passed to symbols, text or points.

Details

To identify the spatial patches, the algorithm starts from the richest density value and considers each sample in decreasing order. It tests whether the current value is spatially close enough to the gravity centre of previously formed patches. if not a new patch is considered, and so on until the last value. Patches of null values are returned with centres as NA and code 0 and their areas are summed.

Value

The number of spatial patches

Note

Function originally developped for the EU project Fisboat, DG-Fish, STREP no 502572. Authors: Woillez, M., and Rivoirard, J. (Geosciences/Mines-ParisTech)

Author(s)

Mathieu Woillez, Ifremer, 2013

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)

SI.patches(db.data, D.min = 100, A.min = 10)
plot(poly.data,col=8,add=TRUE,flag.proj=FALSE,main="Spatial patches")

rm(db.data,poly.data)

---