sp: as.SpatialPolygons.GridTopology – R documentation

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as.SpatialPolygons.GridTopology

Make SpatialPolygons object from GridTopology object

Description

Converts grids of regular rectangles into a SpatialPolygons object, which can be transformed to a different projection or datum with spTransform in package rgdal. The function is not suitable for high-resolution grids. The ordering of the grid cells is as in coordinates() of the same object, and is reported by IDvaluesGridTopology.

Usage

as.SpatialPolygons.GridTopology(grd, proj4string = CRS(as.character(NA)))
IDvaluesGridTopology(obj)
as.SpatialPolygons.SpatialPixels(obj)
IDvaluesSpatialPixels(obj)
HexPoints2SpatialPolygons(hex, dx)

Arguments

`grd`	`GridTopology` object
`proj4string`	object of class CRS-class
`obj`	`SpatialPixels` object
`hex`	`SpatialPoints` object with points that are generated by hexagonal sampling; see spsample
`dx`	spacing of two horizontally adjacent points; if missing, this will be computed from the points

Value

as.SpatialPolygons.GridTopology and as.SpatialPolygons.SpatialPixels return a SpatialPolygons object; IDvaluesGridTopology and IDvaluesSpatialPixels return a character vector with the object grid indices.

Examples

library(lattice)
grd <- GridTopology(cellcentre.offset=c(-175,55), cellsize=c(10,10), cells.dim=c(4,4))
SpP_grd <- as.SpatialPolygons.GridTopology(grd)
plot(SpP_grd)
text(coordinates(SpP_grd), sapply(slot(SpP_grd, "polygons"), function(i) slot(i, "ID")), cex=0.5)
trdata <- data.frame(A=rep(c(1,2,3,4), 4), B=rep(c(1,2,3,4), each=4),
 row.names=sapply(slot(SpP_grd, "polygons"), function(i) slot(i, "ID")))
SpPDF <- SpatialPolygonsDataFrame(SpP_grd, trdata)
spplot(SpPDF)

data(meuse.grid)
gridded(meuse.grid)=~x+y
xx = spsample(meuse.grid,  type="hexagonal", cellsize=200)
xxpl = HexPoints2SpatialPolygons(xx)
image(meuse.grid["dist"])
plot(xxpl, add = TRUE)
points(xx, cex = .5)
## Not run: 
spplot(aggregate(as(meuse.grid[,1:3], "SpatialPolygonsDataFrame"), xxpl,
 areaWeighted=TRUE), main = "aggregated meuse.grid")

## End(Not run)

sp

Classes and Methods for Spatial Data

v1.4-5

GPL (>= 2)

Authors

Edzer Pebesma [aut, cre], Roger Bivand [aut], Barry Rowlingson [ctb], Virgilio Gomez-Rubio [ctb], Robert Hijmans [ctb], Michael Sumner [ctb], Don MacQueen [ctb], Jim Lemon [ctb], Finn Lindgren [ctb], Josh O'Brien [ctb], Joseph O'Rourke [ctb]

Initial release