SpatialGrid function

define spatial grid

defines spatial grid by offset, cell size and dimensions

GridTopology(cellcentre.offset, cellsize, cells.dim)
SpatialPixels(points, tolerance = sqrt(.Machine$double.eps),
                proj4string = CRS(as.character(NA)), round = NULL, grid = NULL)
SpatialGrid(grid, proj4string = CRS(as.character(NA)))
coordinatevalues(obj)
points2grid(points, tolerance = sqrt(.Machine$double.eps), round=NULL)
getGridIndex(cc, grid, all.inside = TRUE)
getGridTopology(obj)
areaSpatialGrid(obj)

Arguments

• cellcentre.offset: numeric; vector with the smallest centroid coordinates for each dimension; coordinates refer to the cell centre
• cellsize: numeric; vector with the cell size in each dimension
• cells.dim: integer; vector with number of cells in each dimension
• points: coordinates, object of class SpatialPoints-class
• grid: grid topology; object of class GridTopology-class ; for calls to SpatialPixels, a value of NULL implies that this will be derived from the point coordinates
• tolerance: precision, used to which extent points are exactly on a grid
• round: default NULL, otherwise a value passed to as the digits argument to round for setting cell size
• proj4string: object of class CRS-class
• obj: object of class or deriving from SpatialGrid-class
• cc: numeric matrix with coordinates
• all.inside: logical; if TRUE and cc points fall outside the grid area, an error message is generated; if FALSE, NA values are generated for such points

Returns

GridTopology returns a value of class GridTopology-class ; SpatialGrid returns an object of class SpatialGrid-class

coordinatevalues returns a list with the unique x-coordinates, the unique y-coordinate, etc. instead of the coordinates of all grid cells

SpatialGrid returns an object of class SpatialGrid-class .

points2grid returns the GridTopology-class from a set of points.

getGridIndex finds the index of a set of point coordinates in a given grid topology, and depending on all.inside setting, generates NA or an error message if points are outside the grid domain.

getGridTopology returns the slot of class GridTopology-class from obj.

areaSpatialGrid returns the spatial area of (the non-missing valued cells of) the grid. For objects of class SpatialGridDataFrame-class

the area refers to cells where any (one or more) of the attribute columns are non-missing valued.

Note

SpatialGrid stores grid topology and may or may not store the coordinates of the actual points, which may form a subset of the full grid. To find out or change this, see fullgrid .

points2grid tries to figure out the grid topology from points. It succeeds only if points on a grid line have constant y column, and points on a grid column have constant x coordinate, etc. In other cases, use signif on the raw coordinate matrices to make sure this is the case.

Author(s)

Edzer Pebesma, edzer.pebesma@uni-muenster.de

See Also

SpatialGrid-class , SpatialGridDataFrame-class ,

Examples

x = GridTopology(c(0,0), c(1,1), c(5,4))
class(x)
x
summary(x)
coordinates(x)
coordinates(GridTopology(c(0,0), c(1,1), c(5,4)))
coordinatevalues(x)
data(meuse.grid)
coordinates(meuse.grid) <- c("x", "y")
points2grid(meuse.grid)
data(meuse.grid)
set.seed(1)
meuse.grid$x <- meuse.grid$x + rnorm(length(meuse.grid$x), 0, 0.002)
meuse.grid$y <- meuse.grid$y + rnorm(length(meuse.grid$y), 0, 0.002)
coordinates(meuse.grid) <- c("x", "y")
#EJP
# points2grid(meuse.grid, tolerance=0.76, round=1)
data(meuse.grid)
a <- which(meuse.grid$x == 180140)
b <- which(meuse.grid$x == 180180)
c <- which(meuse.grid$x == 179260)
d <- which(meuse.grid$y == 332460)
e <- which(meuse.grid$y == 332420)
f <- which(meuse.grid$y == 330740)
meuse.grid <- meuse.grid[-c(a, b, c, d, e, f),]
coordinates(meuse.grid) <- c("x", "y")
points2grid(meuse.grid)
data(meuse.grid)
set.seed(1)
meuse.grid$x <- meuse.grid$x + rnorm(length(meuse.grid$x), 0, 0.002)
meuse.grid$y <- meuse.grid$y + rnorm(length(meuse.grid$y), 0, 0.002)
meuse.grid <- meuse.grid[-c(a, b, c, d, e, f),]
coordinates(meuse.grid) <- c("x", "y")
# EJP
# points2grid(meuse.grid, tolerance=0.69, round=1)