Rasterize points, lines, or polygons
Transfer values associated with 'object' type spatial data (points, lines, polygons) to raster cells.
For polygons, values are transferred if the polygon covers the center of a raster cell. For lines, values are transferred to all cells that are touched by a line. You can combine this behaviour by rasterizing polygons as lines first and then as polygons.
If x represents points, each point is assigned to a grid cell. Points that fall on a border between cells are placed in the cell to the right and/or in the cell below. The value of a grid cell is determined by the values associated with the points and function fun.
## S4 method for signature 'matrix,Raster'
rasterize(x, y, field, fun='last', background=NA,
mask=FALSE, update=FALSE, updateValue='all', filename="", na.rm=TRUE, ...)
## S4 method for signature 'SpatialPoints,Raster'
rasterize(x, y, field, fun='last', background=NA,
mask=FALSE, update=FALSE, updateValue='all', filename="", na.rm=TRUE, ...)
## S4 method for signature 'SpatialLines,Raster'
rasterize(x, y, field, fun='last', background=NA,
mask=FALSE, update=FALSE, updateValue='all', filename="", ...)
## S4 method for signature 'SpatialPolygons,Raster'
rasterize(x, y, field, fun='last', background=NA,
mask=FALSE, update=FALSE, updateValue='all', filename="",
getCover=FALSE, silent=TRUE, ...)x |
points (a SpatialPoints* object, or a two-column matrix (or data.frame)), SpatialLines*, SpatialPolygons*, or an Extent object |
y |
Raster* object |
field |
numeric or character. The value(s) to be transferred. This can be a single number, or a vector of numbers that has the same length as the number of spatial features (points, lines, polygons). If |
fun |
function or character. To determine what values to assign to cells that are covered by multiple spatial features. You can use functions such as If You can also pass multiple functions using a statement like |
background |
numeric. Value to put in the cells that are not covered by any of the features of |
mask |
logical. If |
update |
logical. If |
updateValue |
numeric (normally an integer), or character. Only relevant when |
filename |
character. Output filename (optional) |
na.rm |
If |
getCover |
logical. If |
silent |
Logical. If |
... |
Additional arguments for file writing as for |
RasterLayer or RasterBrick
###############################
# rasterize points
###############################
r <- raster(ncols=36, nrows=18)
n <- 1000
set.seed(123)
x <- runif(n) * 360 - 180
y <- runif(n) * 180 - 90
xy <- cbind(x, y)
# get the (last) indices
r0 <- rasterize(xy, r)
# presence/absensce (NA) (is there a point or not?)
r1 <- rasterize(xy, r, field=1)
# how many points?
r2 <- rasterize(xy, r, fun=function(x,...)length(x))
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 <- data.frame(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 <- spLines(cds1, cds2, cds3)
r <- raster(ncols=90, nrows=45)
r <- rasterize(lines, r)
## Not run:
plot(r)
plot(lines, add=TRUE)
r <- rasterize(lines, r, fun='count')
plot(r)
values(r) <- 1:ncell(r)
r <- rasterize(lines, r, mask=TRUE)
plot(r)
values(r) <- 1
r[lines] <- 10
plot(r)
## End(Not run)
###############################
# 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))
p1 <- list(p1, hole)
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 <- spPolygons(p1, p2, p3)
r <- raster(ncol=90, nrow=45)
r <- rasterize(pols, r, fun=sum)
## Not run:
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)
## End(Not run)Please choose more modern alternatives, such as Google Chrome or Mozilla Firefox.