R: Make SpatialPolygons object from GridTopology object

as.SpatialPolygons.GridTopology {sp}

R Documentation

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

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(getSpPPolygonsLabptSlots(SpP_grd), getSpPPolygonsIDSlots(SpP_grd), 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=getSpPPolygonsIDSlots(SpP_grd))
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)
df = as.data.frame(meuse.grid)[overlay(meuse.grid, xx),]
x = SpatialPolygonsDataFrame(xxpl, df, match.ID = FALSE)
spplot(x["dist"])