ConnCompLabel {mgc}

Connected Components Labelling – Unique Patch Labelling

Description

ConnCompLabel is a 1 pass implementation of connected components labelling. Here it is applied to identify disjunt patches within a distribution.

The raster matrix can be a raster of class 'asc' (adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package).

Usage

ConnCompLabel(mat)

Arguments

mat

is a binary matrix of data with 0 representing background and 1 representing environment of interest. NA values are acceptable. The matrix can be a raster of class 'asc' (this & adehabitat package), 'RasterLayer' (raster package) or 'SpatialGridDataFrame' (sp package)

Value

A matrix of the same dim and class of mat in which unique components (individual patches) are numbered 1:n with 0 remaining background value.

Author(s)

Jeremy VanDerWal [e-mail]

References

Chang, F., C.-J. Chen, and C.-J. Lu. 2004. A linear-time component-labeling algorithm using contour tracing technique. Comput. Vis. Image Underst. 93:206-220.

Examples

#define a simple binary matrix
tmat = { matrix(c( 0,0,0,1,0,0,1,1,0,1,
                   0,0,1,0,1,0,0,0,0,0,
                   0,1,NA,1,0,1,0,0,0,1,
                   1,0,1,1,1,0,1,0,0,1,
                   0,1,0,1,0,1,0,0,0,1,
                   0,0,1,0,1,0,0,1,1,0,
                   1,0,0,1,0,0,1,0,0,1,
                   0,1,0,0,0,1,0,0,0,1,
                   0,0,1,1,1,0,0,0,0,1,
                   1,1,1,0,0,0,0,0,0,1),nr=10,byrow=TRUE) }

#do the connected component labelling
ccl.mat = ConnCompLabel(tmat)
ccl.mat
image(t(ccl.mat[10:1,]),col=c('grey',rainbow(length(unique(ccl.mat))-1)))