SpatialVx (version 0.1-2)

Cindex: Connectivity Index

Description

Calculate the connectivity index of an image

Usage

Cindex(x, thresh = NULL, connect.method = "C")

Arguments

x

m X n numeric matrix for which the connectivity index is to be calculated.

thresh

Set values under (strictly less than) this threshold to zero, and calculate the connectivity index for the resulting image. If NULL, no threshold is applied.

connect.method

character string giving the method argument for the connected function of package spatstat. This must be one of "C" or "interpreted. See the help file for connected for more details.

Value

• single numeric giving the connectivity index.

Details

The connectivity index is introduced in AghaKouchak et al. (2011), and is designed to automaticlaly determine how connected an image is. It is defined by

Cindex = 1 - (NC - 1)/(sqrt(NP) + NC),

where 0 <= 1="" cindex="" <="1" is="" the="" connectivity="" index="" (values="" close="" to="" zero="" are="" less="" connected,="" and="" values="" more="" connected),="" np="" number="" of="" nonzero="" pixels,="" nc="" isolated="" clusters.="" p="">

The function 'connected' from package 'spatstat' is used to identify the number of isolated clusters.

References

AghaKouchak, A., N. Nasrollahi, J. Li, B. Imam, and S. Sorooshian, 2011: Geometrical characterization of precipitation patterns. J. Hydrometerology, 12, 274--285, DOI: 10.1175/2010JHM1298.1

See Also

connected, as.im, Sindex, Aindex

Examples

data(geom000)
Cindex(geom000)

data(pert000)
Cindex(pert000)