velox (version 0.2.0)

VeloxRaster_rasterize: Rasterize Polygons or Lines

Description

Rasterizes a collection of polygons or lines, i.e. assigns the values in the field column of the SPDF to the raster cells intersecting with the respective geometry.

Arguments

spdf

A sf POLYGON or MULTIPOLYGON object, a sf LINE or MULTILINE object, a SpatialPolygonsDataFrame object, or a SpatialLinesDataFrame object.

field

A character string corresponding to the name of a numeric column in spdf.

band

A positive integer denoting the ID of the band where the rasterized values are written.

background

Optional. A numeric value assigned to all background cells.

small

Boolean. If TRUE and spdf contains polygons, then intersections for small (or oddly shaped) polygons that do not intersect with any cell centroid are established by intersecting the small polygon with the entire (boxed) cells.

Value

Void.

Details

Note that rasterization is performed sequentially. Hence, cells being contained by multiple polygons are assigned the value of the last polygon in the spdf object. If argument small = TRUE, then the values of small polygons are assigned last.

If spdf contains polygons, then cell-polygon intersections are calculated based on cell centroids (but see argument small). If spdf contains lines, then regular cell-line intersections are calculated.

Examples

# NOT RUN {
## Make VeloxRaster
mat <- matrix(0, 10, 10)
vx <- velox(mat, extent=c(0,1,0,1), res=c(0.1,0.1), crs="+proj=longlat +datum=WGS84 +no_defs")
## Make SpatialPolygonsDataFrame
library(sp)
library(rgeos)
coord <- cbind(0.5, 0.5)
spoint <- SpatialPoints(coords=coord)
spols <- gBuffer(spgeom=spoint, width=0.25)
spdf <- SpatialPolygonsDataFrame(Sr=spols, data=data.frame(value=1), match.ID=FALSE)
## Rasterize, set background to -1
vx$rasterize(spdf=spdf, field="value", background=-1)

# }