sp (version 0.8-4)

image.SpatialGridDataFrame: image gridded spatial data, or convert to format for image

Description

Convert gridded data in SpatialGridDataFrame to image format; call image on data in SpatialGridDataFrame format

Usage

image.SpatialGridDataFrame(x, attr = 1, xcol = 1, ycol = 2, 
	red=NULL, green=NULL, blue=NULL, asp = 1, axes = FALSE, xlim = NULL,
	ylim = NULL, add = FALSE, ...)
as.image.SpatialGridDataFrame(x, xcol = 1, ycol = 2)

Arguments

x
object of class SpatialGridDataFrame
attr
column number of attribute variable; this may be the column name in the data.frame of data (as.data.frame(data)), or a column number
xcol
column number of x-coordinate, in the coordinate matrix
ycol
column number of y-coordinate, in the coordinate matrix
red,green,blue
columns names or numbers given instead of the attr argument when the data represent an image encoded in three colour bands on the 0-255 integer scale; all three columns must be given in this case, and the attribute values will be constructed
asp
aspect ratio of unit x and unit y axis
axes
logical; should coordinate axes be drawn?
xlim
x-axis limits
ylim
y-axis limits
add
logical; if FALSE, the image is added to the plot layout setup by plot(as(x, "Spatial"),axes=axes,xlim=xlim,ylim=ylim,asp=asp) which sets up axes and plotting region; if TRUE, the image is added to the existing plot.
...
arguments passed to image, see examples

Value

  • as.image.SpatialGridDataFrame returns the list with elements x and y, containing the coordinates of the cell centres of a matrix z, containing the attribute values in matrix form as needed by image.

See Also

image.default, SpatialGridDataFrame-class, levelplot in package lattice

Examples

Run this code
data(meuse.grid)
coordinates(meuse.grid) = c("x", "y") # promote to SpatialPointsDataFrame
gridded(meuse.grid) = TRUE            # promote to SpatialGridDataFrame
image(meuse.grid["dist"], main = "Distance to river Meuse")
data(meuse)
coordinates(meuse) = c("x", "y")
points(coordinates(meuse), pch = "+")
data(Rlogo)
d = dim(Rlogo)
cellsize = abs(c(gt[2],gt[6]))
cells.dim = c(d[1], d[2]) # c(d[2],d[1])
cellcentre.offset = c(x = gt[1] + 0.5 * cellsize[1], y = gt[4] - (d[2] - 0.5) * abs(cellsize[2]))
grid = GridTopology(cellcentre.offset, cellsize, cells.dim)
df = as.vector(Rlogo[,,1])
for (band in 2:d[3]) df = cbind(df, as.vector(Rlogo[,,band]))
df = as.data.frame(df)
names(df) = paste("band", 1:d[3], sep="")
Rlogo <- SpatialGridDataFrame(grid = grid, data = df)
summary(Rlogo)
image(Rlogo, red="band1", green="band2", blue="band3")

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