Write classified raster with its symbology

Question

I've classified lots of rasters and I'd like to write them with the symbology I've defined.

Here is the kind of raster I'm dealing with:

library(raster)
library(rasterVis)
r <- raster(nrow=10, ncol=10)
r[] = 1
r[51:100] = 3
r[3:6, 1:5] = 5
r <- ratify(r)

rat <- levels(r)[[1]]
rat$landcover <- c('Pine', 'Oak', 'Meadow')
rat$class <- c('A1', 'B2', 'C3')
levels(r) <- rat
levelplot(r, col.regions=c('palegreen', 'midnightblue', 'indianred1'))

Answer 1

I found the solution on this awesome website

addColorTable <- function(inRstName, outRstName, rat.df){
  library(rgdal)
  r<- readGDAL(inRstName)
  rat.df$color<- as.character(rat.df$color)
  rat.df$attribute<- as.character(rat.df$attribute)
  outRst <- writeGDAL(r, outRstName, type="Byte", 
  colorTable=list(rat.df$color), 
  catNames=list(rat.df$attribute), mvFlag=11L)
  return(raster(outRst))
}


library(rgdal)
library(raster)

# create dummy data set
r <- raster(nrow=10, ncol=10)
r[] <- 0
r[51:100] <- 1
r[3:6, 1:5] <- 2
r[1, 1] <- 3
writeRaster(r,'dummy_raster.tif',overwrite=T)

# This defines the values, the color and the attribute
valT <- c(0,1,2,3)
colT <-  c("#FF0000", "#FF9900" ,"#99FF00","#0000FF")
attT <- c('Forest','Water body','City','Cropland')
rat.df <- data.frame(value=valT,color=colT,attribute=attT)

# apply the magic function
rnew <- addColorTable('dummy_raster.tif', 'dummy_raster_with_symbology.tif', rat.df)

# plot the results and tadaaaa
spplot(rnew, col.regions=colT)

Answer 2

You can do this with raster version 2.3-40 or higher. Note that the classes should be sequential from 0,1,2,...

library(raster)
library(rasterVis)
r <- raster(nrow=10, ncol=10)
r[] = 0
r[51:100] = 1
r[3:6, 1:5] = 2
r <- ratify(r)

rat <- levels(r)[[1]]
rat$landcover <- c('Pine', 'Oak', 'Meadow')
rat$class <- c('A1', 'B2', 'C3')
levels(r) <- rat

x <- writeRaster(r, 'test.tif', overwrite=TRUE)
levelplot(x, col.regions=c('palegreen', 'midnightblue', 'indianred1'))