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

It did not work for me. I used this script to split the color scale and select the one more suitable according to my data:

plot(d, col=rev(heat.colors(8, alpha = 1)), breaks = seq(0, 0.40, by = 0.05))

Answer 2

Easy solution now is to use the zlim option.

plot( d, col=rev( rainbow( 99, start=0,end=1 ) ),zlim=c(0,1) )

Answer 3

A pretty simple solution that should usually work (e.g. with the "plot" function in the raster package) is to set "z axis" limits (which control the colors and the color legend).

E.g. you can do something like: plot(d, zlim=c(0,1))

where d is a stacked raster object. Or, if you have a bunch of separate rasters d1, d2, d2..., you can just do: plot(d1, zlim=c(0,1)) plot(d2, zlim=c(0,1)) plot(d3, zlim=c(0,1)) ...

Answer 4

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)

Answer 5

Since the image::raster function specifies that the image::base arguments can be passed (and suggests that image::base is probably used), wouldn't you just specify the same col= and breaks= arguments to all calls to image::raster? You do need to get the breaks and the col arguments "in sync". The number of colors needs to be one less than the number of breaks. The example below is based on the classic volcano data and the second version shows how a range of values can be excluded from an image:

 x <- 10*(1:nrow(volcano))
 y <- 10*(1:ncol(volcano))
 image(x, y, volcano, col = terrain.colors( length(seq(90, 200, by = 5))-1), axes = FALSE, breaks= seq(90, 200, by = 5) )
 axis(1, at = seq(100, 800, by = 100))
 axis(2, at = seq(100, 600, by = 100))
 box()
 title(main = "Maunga Whau Volcano", font.main = 4)



 x <- 10*(1:nrow(volcano))
 y <- 10*(1:ncol(volcano))
 image(x, y, volcano, col = terrain.colors( length(seq(150, 200, by = 5))-1), axes = FALSE, breaks= seq(150, 200, by = 5) )
 axis(1, at = seq(100, 800, by = 100))
 axis(2, at = seq(100, 600, by = 100))
 box()
 title(main = "Maunga Whau Volcano Restricted to elevations above 150", font.main = 4)

A specific example would aid this effort.

Answer 6

Added as an answer in response to @Tomas

The answer I ended up using is:

plot( d, col=rev( rainbow( 99, start=0,end=1 ) ), 
    breaks=seq(min(minValue( d )),max(maxValue(d)),length.out=100) )