sp (version 0.9-78)

gridded-methods: specify spatial data as being gridded, or find out whether they are

Description

returns logical (TRUE or FALSE) telling whether the object is gridded or not; in assignment promotes a non-gridded structure to a gridded one, or demotes a gridded structure back to a non-structured one.

Usage

gridded(obj)
	gridded(obj) <- TRUE
	fullgrid(obj)
	fullgrid(obj) <- TRUE
	gridparameters(obj)

Arguments

obj

object deriviving from class "Spatial" (for gridded), or object of class SpatialGridDataFrame-class (for fullgrid and gridparameters)

Value

• if obj derives from class Spatial, gridded(object) will tell whether it is has topology on a regular grid; if assigned TRUE, if the object derives from SpatialPoints and has gridded topology, grid topology will be added to object, and the class of the object will be promoted to SpatialGrid-class or SpatialGridDataFrame-class

  fullgrid returns a logical, telling whether the grid is full and ordered (i.e., in full matrix form), or whether it is not full or unordered (i.e. a list of points that happen to lie on a grid. If assigned, the way the points are stored may be changed. Changing a set of points to full matrix form and back may change the original order of the points, and will remove duplicate points if they were present.

  gridparameters returns, if obj inherits from SpatialGridDataFrame its grid parameters, else it returns numeric(0). The returned value is a data.frame with three columns, named cellcentre.offset ("lower left cell centre coordinates"), cellsize, and cells.dim (cell dimension); the rows correspond to the spatial dimensions.

Examples

# just 9 points on a grid:
x <- c(1,1,1,2,2,2,3,3,3)
y <- c(1,2,3,1,2,3,1,2,3)
xy <- cbind(x,y)
S <- SpatialPoints(xy)
class(S)
plot(S)
gridded(S) <- TRUE
gridded(S)
class(S)
summary(S)
plot(S)
gridded(S) <- FALSE
gridded(S)
class(S)

# data.frame
data(meuse.grid)
coordinates(meuse.grid) <- ~x+y
gridded(meuse.grid) <- TRUE
plot(meuse.grid) # not much good
summary(meuse.grid)