image.SpatialGridDataFrame: Image or contour method for gridded spatial data; convert to and from image data structure

Description

Create image for gridded data in SpatialGridDataFrame or SpatialPixelsDataFrame objects.

Usage

# S3 method for SpatialGridDataFrame
image(x, attr = 1, xcol = 1, ycol = 2, 
	col = heat.colors(12), red=NULL, green=NULL, blue=NULL,
        axes = FALSE, xlim = NULL,
	ylim = NULL, add = FALSE, ..., asp = NA, setParUsrBB=FALSE,
        interpolate = FALSE, angle = 0, 
	useRasterImage = !(.Platform$GUI[1] == "Rgui" &&
        getIdentification() == "R Console") && missing(breaks), breaks,
	zlim = range(as.numeric(x[[attr]])[is.finite(x[[attr]])]))
# S3 method for SpatialPixelsDataFrame
image(x, ...) 
# S3 method for SpatialPixels
image(x, ...) 
# S3 method for SpatialGridDataFrame
contour(x, attr = 1, xcol = 1, ycol = 2,
	col = 1, add = FALSE, xlim = NULL, ylim = NULL, axes = FALSE,
         ..., setParUsrBB = FALSE)
# S3 method for SpatialPixelsDataFrame
contour(x, ...) 
as.image.SpatialGridDataFrame(x, xcol = 1, ycol = 2, attr = 1)
image2Grid(im, p4 = as.character(NA), digits=10)

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.

Arguments

x: object of class SpatialGridDataFrame
attr: column 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
col: a vector of colors
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
zlim: data limits for plotting the (raster, attribute) values
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
asp: aspect ratio to be used for plot
setParUsrBB: default FALSE, see Spatial-class for further details
useRasterImage: if TRUE, use rasterImage to render the image if available; for legacy rendering set FALSE; should be FALSE on Windows SDI installations
breaks: class breaks for coloured values
interpolate: default FALSE, a logical vector (or scalar) indicating whether to apply linear interpolation to the image when drawing, see rasterImage
angle: default 0, angle of rotation (in degrees, anti-clockwise from positive x-axis, about the bottom-left corner), see rasterImage
im: list with components named x, y, and z, as used for image
p4: CRS object, proj4 string
digits: default 10, number of significant digits to use for checking equal row/column spacing

Author

Edzer Pebesma

Examples

Run this code

data(meuse.grid)
coordinates(meuse.grid) = c("x", "y") # promote to SpatialPointsDataFrame
gridded(meuse.grid) = TRUE            # promote to SpatialGridDataFrame
data(meuse)
coordinates(meuse) = c("x", "y")
image(meuse.grid["dist"], main = "Distance to river Meuse")
points(coordinates(meuse), pch = "+")
image(meuse.grid["dist"], main = "Distance to river Meuse",
 useRasterImage=TRUE)
points(coordinates(meuse), pch = "+")

# color scale:
layout(cbind(1,2), c(4,1),1)
image(meuse.grid["dist"])
imageScale(meuse.grid$dist, axis.pos=4, add.axis=FALSE)
axis(4,at=c(0,.2,.4,.8), las=2)

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")
image(Rlogo, red="band1", green="band2", blue="band3",
 useRasterImage=FALSE)
is.na(Rlogo$band1) <- Rlogo$band1 == 255
is.na(Rlogo$band2) <- Rlogo$band2 == 255
is.na(Rlogo$band3) <- Rlogo$band3 == 255
Rlogo$i7 <- 7
image(Rlogo, "i7")
image(Rlogo, red="band1", green="band2", blue="band3", add=TRUE)

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