R: boundaries (edges) detection

boundaries {raster} | R Documentation

## boundaries (edges) detection

### Description

Detect boundaries (edges). boundaries are cells that have more than one class in the 4 or 8 cells surrounding it, or, if `classes=FALSE`, cells with values and cells with `NA`.

### Usage

    ## S4 method for signature 'RasterLayer'
    boundaries(x, type='inner', classes=FALSE, directions=8, asNA=FALSE, filename="", ...)

### Arguments

`x` | RasterLayer object
`type` | character. 'inner' or 'outer'
`classes` | character. Logical. If `TRUE` all different values are (after rounding) distinguished, as well as `NA`. If `FALSE` (the default) only edges between `NA` and non-`NA` cells are considered
`directions` | integer. Which cells are considered adjacent? Should be 8 (Queen's case) or 4 (Rook's case)
`asNA` | logical. If `TRUE`, non-edges are returned as `NA` instead of zero
`filename` | character. Filename for the output RasterLayer (optional)
`...` | additional arguments as for `writeRaster`

### Value

RasterLayer. Cell values are either 1 (a border) or 0 (not a border), or `NA`

### Note

'edge' is obsolete and should not be used. It will be removed from this pacakge

### See Also

`focal`, `clump`

### Examples

    r <- raster(nrow=18, ncol=36, xmn=0)
    r[150:250] <- 1
    r[251:450] <- 2
    plot( boundaries(r, type='inner') )
    plot( boundaries(r, type='outer') )
    plot( boundaries(r, classes=TRUE) )

[Package raster version 2.6-7 Index]