Raster to polygons conversion

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Description

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).

Usage

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

Arguments

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

Details

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}

Value

SpatialPolygonsDataFrame

Examples

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r <- raster(nrow=18, ncol=36)
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')

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