R: Detect clumps

clump {raster} | R Documentation

## Detect clumps

### Description

Detect clumps (patches) of connected cells. Each clump gets a unique ID. NA and zero are used as background values (i.e. these values are used to separate clumps). You can use queen's or rook's case, using the `directions` argument. For larger files that are processed in chunks, the highest clump number is not necessarily equal to the number of clumps (unless you use argument `gaps=FALSE`).

### Usage

    ## S4 method for signature 'RasterLayer'
    clump(x, filename="", directions=8, gaps=TRUE, ...)

### Arguments

`x` | RasterLayer
`filename` | Character. Filename for the output RasterLayer (optional)
`directions` | Integer. Which cells are considered adjacent? Should be 8 (Queen's case) or 4 (Rook's case)
`gaps` | Logical. If `TRUE` (the default), there may be 'gaps' in the chunk numbers (e.g. you may have clumps with IDs 1, 2, 3 and 5, but not 4). If it is `FALSE`, these numbers will be recoded from 1 to n (4 in this example)
`...` | Additional arguments as for `writeRaster`

### Value

RasterLayer

### Note

This function requires that the igraph package is available.

### Author(s)

Robert J. Hijmans and Jacob van Etten

### Examples

    r <- raster(ncols=12, nrows=12)
    set.seed(0)
    r[] <- round(runif(ncell(r))*0.7 )
    rc <- clump(r)
    freq(rc)
    plot(rc)

[Package raster version 2.6-7 Index]