How can I create raster plots with the same colour scale in R

Question

I\'m creating some maps from raster files using the \"raster\" package in R. I\'d like to create comparison rasters, showing several maps side by side. It\'s important for this

Answer 1

There is more work to be done here in 'raster' but here is a hack:

 library(raster)
 r1 <- r2 <- r3 <- raster(ncol=10, nrow=10)
 r1[] <- runif(ncell(r1))
 r2[] <- runif(ncell(r2)) / 2
 r3[] <- runif(ncell(r3)) * 1.5
 r3 <- min(r3, 1)
 s <- stack(r1, r2, r3)


 brk <- c(0, 0.25, 0.5, 0.75, 1)
 par(mfrow=c(1,3))
 plot(r1, breaks=brk, col=rainbow(4), legend=F)
 plot(r1, breaks=brk, col=rainbow(4), legend.only=T, box=F)
 plot(r2, breaks=brk, col=rainbow(4), legend=F)
 plot(r1, breaks=brk, col=rainbow(4), legend.only=T, box=F)
 plot(r3, breaks=brk, col=rainbow(4), legend=F)
 plot(r1, breaks=brk, col=rainbow(4), legend.only=T, box=F)

You can also use the spplot function (sp package)

 s <- stack(r1, r2, r3) 
 sp <- as(s, 'SpatialGridDataFrame')
 spplot(sp)

You can also send the values to ggplot (search the r-sig-geo archives for examples) If your RasterLayer links to a very large file, you might first do, before going to ggplot

r <- sampleRegular(r, size=100000, asRaster=TRUE) 

and then perhaps

m <- as.matrix(r)