rasterToPolygons: Raster to polygons conversion
In raster: Geographic Data Analysis and Modeling

Description Usage Arguments Details Value Examples

Raster to polygons conversion. Cells with NA are not converted. A function can be used to select a subset of the raster cells (by their values).

1	rasterToPolygons(x, fun=NULL, n=4, na.rm=TRUE, digits=12, dissolve=FALSE)

`x`	Raster* object
`fun`	function to select a subset of raster values (only allowed if `x` has a single layer)
`n`	integer. The number of nodes for each polygon. Only 4, 8, and 16 are allowed
`na.rm`	If `TRUE`, cells with `NA` values in all layers are ignored
`digits`	number of digits to round the coordinates to
`dissolve`	logical. If `TRUE`, polygons with the same attribute value will be dissolved into multi-polygon regions. This option requires the rgeos package

fun should be a simple function returning a logical value.

E.g.: fun=function(x){x==1} or fun=function(x){x>3 & x<6}

SpatialPolygonsDataFrame

 
r <- raster(nrow=18, ncol=36)
values(r) <- runif(ncell(r)) * 10
r[r>8] <- NA
pol <- rasterToPolygons(r, fun=function(x){x>6})

#plot(r > 6)
#plot(pol, add=TRUE, col='red')