raster (version 1.9-70)

rasterize: Rasterize points, lines, or polygons

Description

Transfer values associated with 'vector' type spatial data (points, lines, polygons) to the spatially overlapping raster cells. For polygons, 'spatially overlapping' means that the polygon must cover the center of a raster cell. All cells that are touched by a line are considered to be overlapping. Points that fall on a border between cells are placed in the cell to the right and/or in the cell below.

Usage

rasterize(x, y, ...)

Arguments

x

points (a SpatialPoints* object, or a two-column matrix), SpatialLines*, SpatialPolygons*, or an Extent object

y

Raster* object

...

Additional arguments, see under Details

Value

• RasterLayer or RasterBrick

See Also

extract

Examples

###############################
# rasterize points
###############################
r <- raster(ncols=36, nrows=18)
n <- 1000
x <- runif(n) * 360 - 180
y <- runif(n) * 180 - 90
xy <- cbind(x, y)
# point or not?
r1 <- rasterize(xy, r)
# how many points?
r2 <- rasterize(xy, r, fun=sum)
vals <- runif(n)
# sum of the values associated with the points
r3 <- rasterize(xy, r, vals, fun=sum)

# with a SpatialPointsDataFrame
vals <- 1:n
p <- as.data.frame(cbind(xy, name=vals))
coordinates(p) <- ~x+y
r <- rasterize(p, r, 'name', fun=min)
#r2 <- rasterize(p, r, 'name', fun=max)
#plot(r, r2, cex=0.5)

###############################
# rasterize lines
###############################
cds1 <- rbind(c(-180,-20), c(-140,55), c(10, 0), c(-140,-60))
cds2 <- rbind(c(-10,0), c(140,60), c(160,0), c(140,-55))
cds3 <- rbind(c(-125,0), c(0,60), c(40,5), c(15,-45))

lines <- SpatialLines(list(Lines(list(Line(cds1)), "1"), Lines(list(Line(cds2)), "2"), Lines(list(Line(cds3)), "3") ))

r <- raster(ncols=90, nrows=45)
r <- rasterize(lines, r)

plot(r)
plot(lines, add=TRUE)

r <- rasterize(lines, r, fun='count')
plot(r)

r[] <- 1:ncell(r)
r <- rasterize(lines, r, mask=TRUE)
plot(r)

r[] <- 1
r[lines] <- 10
plot(r)

###############################
# rasterize polygons
###############################

p1 <- rbind(c(-180,-20), c(-140,55), c(10, 0), c(-140,-60), c(-180,-20))
hole <- rbind(c(-150,-20), c(-100,-10), c(-110,20), c(-150,-20))
p2 <- rbind(c(-10,0), c(140,60), c(160,0), c(140,-55), c(-10,0))
p3 <- rbind(c(-125,0), c(0,60), c(40,5), c(15,-45), c(-125,0))
pols <- SpatialPolygons( list(  Polygons(list(Polygon(p1), Polygon(hole)), 1), Polygons(list(Polygon(p2)), 2), Polygons(list(Polygon(p3)), 3)))
pols@polygons[[1]]@Polygons[[2]]@hole <- TRUE

r <- raster(ncol=180, nrow=90)
r <- rasterize(pols, r, fun='sum')

plot(r)
plot(pols, add=T)

# add a polygon
p5 <- rbind(c(-180,10), c(0,90), c(40,90), c(145,-10),  c(-25, -15), c(-180,0), c(-180,10))
addpoly <- SpatialPolygons(list(Polygons(list(Polygon(p5)), 1)))
addpoly <- as(addpoly, "SpatialPolygonsDataFrame")
addpoly@data[1,1] <- 10
r2 <- rasterize(addpoly, r, field=1, update=TRUE, updateValue="NA")
plot(r2)
plot(pols, border="blue", lwd=2, add=TRUE)
plot(addpoly, add=TRUE, border="red", lwd=2)

# get the percentage cover of polygons in a cell
r3 <- raster(ncol=36, nrow=18)
r3 <- rasterize(pols, r3, getCover=TRUE)