| image.SpatialGridDataFrame {sp} | R Documentation |
Convert gridded data in SpatialGridDataFrame to image format; call image on data in SpatialGridDataFrame format. The aspect ratio is set as either 1 for projected data, or stretched by distance from Equator for geographical coordinates.
## S3 method for class 'SpatialGridDataFrame':
image(x, attr = 1, xcol = 1, ycol = 2,
red=NULL, green=NULL, blue=NULL, axes = FALSE, xlim = NULL,
ylim = NULL, add = FALSE, ..., setParUsrBB=FALSE)
## S3 method for class 'SpatialPixelsDataFrame':
image(x, ...)
## S3 method for class 'SpatialGridDataFrame':
contour(x, attr = 1, xcol = 1, ycol = 2,
add = FALSE, xlim = NULL, ylim = NULL, axes = FALSE, ..., setParUsrBB = FALSE)
## S3 method for class 'SpatialPixelsDataFrame':
contour(x, ...)
as.image.SpatialGridDataFrame(x, xcol = 1, ycol = 2)
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 using function rgb |
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 |
setParUsrBB |
default FALSE, see Spatial-class for further details |
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.
Providing xcol and ycol attributes seems obsolete,
and it is for 2D data, but it may provide opportunities for plotting
certain slices in 3D data. I haven't given this much thought yet.
filled.contour seems to misinterpret the coordinate values, if we take the image.default manual page as the reference.
Edzer J. Pebesma
image.default, SpatialGridDataFrame-class,
levelplot in package lattice
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")