plot: Plot a Raster* object

Description

Plot (that is, make a map of) the values of a Raster* object, or make a scatterplot of their values. Points, lines, and polygons can be drawn on top of a map using plot(..., add=TRUE), or with functions like points, lines, polygons See the rasterVis package for more advanced (trellis/lattice) plotting of Raster* objects.

Usage

## S3 method for class 'Raster,ANY':
plot(x, y, col=rev(terrain.colors(255)), maxpixels=500000, alpha=1,
   colNA=NA, add=FALSE, ext=NULL, useRaster=TRUE, interpolate=FALSE, addfun=NULL, nc, nr, ...)


## S3 method for class 'Raster,Raster':
plot(x, y, maxpixels=100000, cex=0.1, ...)

Arguments

Raster* object

If x is a RasterStack or RasterBrick: integer, character (layer name(s)), or missing to select which layer(s) to plot. If missing, all RasterLayers in the RasterStack will be plotted (up to a maximum of 16). Or another Raster* object of the s

col

A color palette, i.e. a vector of n contiguous colors generated by functions like rainbow, heat.colors, topo.colors,

maxpixels

Maximum number of pixels used

useRaster

If TRUE, the rasterImage function is used for plotting. Otherwise the image function is used. This can be useful if rasterImage does not work well on your system (see note)

alpha

Number between 0 and 1 to set transparency. 0 is entirely transparent, 1 is not transparent

colNA

The color to use for the background (default is transparent)

add

Logical. Add to current plot?

ext

An extent object to zoom in a region (see also zoom and crop(x, drawExtent())

interpolate

Logical. Should the image be interpolated (smoothed)?

addfun

Function to add additional items such as points or polygons to the plot (map). Typically containing statements like "points(xy); plot(polygons, add=TRUE)". This is particularly useful to add something to each map when plotting a multi-layer Raste

...

Graphical parameters. Any argument that can be passed to image.plot and to plot, such as axes=FALSE, main='title', ylab='latitude'

Optional. The number of columns to divide the plotting device in (when plotting multiple layers in a RasterLayer or RasterBrick object)

Optional. The number of rows to divide the plotting device in (when plotting multiple layers in a RasterLayer or RasterBrick object)

cex

Symbol size for scatter plots

Details

Most of the code for this function was taken from image.plot (fields package). Raster objects with a color-table (e.g. a graphics file) are plotted according to the color table.

Examples

Run this code

# RasterLayer
r <- raster(nrows=10, ncols=10)
r <- setValues(r, 1:ncell(r))
plot(r)

e <- extent(r)
plot(e, add=TRUE, col='red', lwd=4)
e <- e / 2
plot(e, add=TRUE, col='red')


# Scatterplot of 2 RasterLayers
r2 <- sqrt(r)
plot(r, r2)

# Multi-layer object (RasterStack / Brick)
s <- stack(r, r2, r/r)
plot(s, 2)
plot(s)

# two objects, different range, one scale:
r[] <- runif(ncell(r))
r2 <- r/2
brks <- seq(0, 1, by=0.1) 
nb <- length(brks)-1 
par(mfrow=c(1,2))
plot(r, breaks=brks, col=rev(terrain.colors(nb)), lab.breaks=brks, zlim=c(0,1)) 
plot(r2, breaks=brks, col=rev(terrain.colors(nb)), lab.breaks=brks, zlim=c(0,1)) 


# breaks and labels
x <- raster(nc=10, nr=10)
x[] <- runif(ncell(x))
brk <- c(0, 0.25, 0.75, 1)
arg <- list(at=c(0.12,0.5,0.87), labels=c("Low","Med.","High"))
plot(x, col=terrain.colors(3), breaks=brk)
plot(x, col=terrain.colors(3), breaks=brk, axis.args=arg)
par(mfrow=c(1,1))

# color ramp
plot(x, col=colorRampPalette(c("red", "white", "blue"))(255))

# adding random points to the map
xy <- cbind(-180 + runif(10) * 360, -90 + runif(10) * 180)
points(xy, pch=3, cex=5)

# for SpatialPolygons do
# plot(pols, add=TRUE)

# adding the same points to each map of each layer of a RasterStack
fun <- function() {
	points(xy, cex=2)
	points(xy, pch=3, col='red')
}
plot(s, addfun=fun)

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