erase function

Erase parts of a SpatialPolygons* or SpatialLines* object. The inverse of this can be done with intersect

Erase parts of a SpatialPolygons* or SpatialLines* object with a SpatialPolygons* object methods

## S4 method for signature 'SpatialPolygons,SpatialPolygons'
erase(x, y, ...)

## S4 method for signature 'SpatialLines,SpatialPolygons'
erase(x, y, ...)

Arguments

• x: SpatialPolygons or SpatialLines object
• y: SpatialPolygons object
• ...: Additional arguments (none)

Returns

Spatial*

See Also

The equivalent for raster data is mask

Examples

# erase parts of polygons with other polygons
p <- shapefile(system.file("external/lux.shp", package="raster"))
b <- as(extent(6, 6.4, 49.75, 50), 'SpatialPolygons')
crs(b) <- crs(p)
e <- erase(p, b)
plot(e)

        
# erase parts of lines with polygons    
        r <- raster(extent(p) +c(-.1,.1,-.1,.1), crs=crs(p))
        start <- xyFromCell(r, cellFromCol(r, 1))
        end <- xyFromCell(r, cellFromCol(r, ncol(r)))
        lines <- do.call(spLines, lapply(1:10, function(i)rbind(start[i,], end[i,])))
        crs(lines) <- crs(p)
        
        e2 <- erase(lines, p)
        plot(p)
        lines(lines, col='blue', lwd=4, lty=3)
        lines(e2, col='red', lwd=2)