Counter-intuitive to all the other questions about splitting raster bands, I would like to split my single-band raster into a multiband raster stack based on the values given in each pixel (range from 1 to 11). Therefore, I would like to conditionally extract pixels based on their values and place them in an individual band. Basically:

band1 <- (if rastervalue == 1)
band2 <- (if rastervalue == 2)
band11 <- (if rastervalue == 11)

stacked <- stack(band1,band2,...band11)

Here is the overview of the data:

class      : RasterLayer 
dimensions : 25658, 15349, 393824642  (nrow, ncol, ncell)
resolution : 249.9999, 249.9999  (x, y)
extent     : -15191755, -11354506, 8399516, 14814014  (xmin, xmax, ymin, ymax)
crs        : +proj=merc +a=6378137 +b=6378137 +lat_ts=0 +lon_0=0 +x_0=0 +y_0=0 +k=1 +units=m +nadgrids=@null +wktext +no_defs 
values     : 1, 11  (min, max)

I have tried to do the following:

data <- raster("path.tif")
band1 = data[data != 1] = NA
band2 = data[data != 2] = NA
band11 = data[data != 11] = NA
stacked <- stack(band1,band2,...band11)

But, I get raster layers of NA for all the bands I create How can I do that in R?

  • 1
    Your code stomps on data when you do data[data!=1]=NA and then returns the value of that expression - not the new value of data - to store into band1. And the value of that expression is NA. You could do it by running in a local scope: band1 = local({data[data!=1]=NA;data}) which leaves the main data object unchanged. Or see my answer!
    – Spacedman
    Sep 23 at 12:49
  • Thanks. That is a good observation, I changed it and that also help. However, the answer from @Spacedman definitely did the job for me!
    – Thomas
    Sep 23 at 13:31

Test raster with numbers 1 to 6 twice:

> r = raster(matrix(1:6, 3,4))

Loop over unique values in r, making a raster from each value, then feed to stack via do.call to make a stack:

> s = do.call(stack, lapply(unique(r[]), function(v){r==v}))
> plot(s)

enter image description here

I'm not sure if you want layers of TRUE/FALSE (1/0) or if you want to put the v values in the layer and NA elsewhere. You can make the function anything you like.

This does zeroes and v values:

s = do.call(stack, lapply(unique(r[]), function(v){(r==v)*v}))

This does NA and v values (but I can't help thinking there's an easier way):

s = do.call(stack, lapply(unique(r[]), function(v){t=r;t[]=NA;t[r==v]=v;t}))

enter image description here

Inspired by my comment on local scoped data, this would be the "easier" way - r is scoped within the function so doesn't change the global r here:

s = do.call(stack, lapply(unique(r[]), function(v){r[r!=v]=NA;r}))

If you know in advance the values then replace unique(r[]) with a vector of the values, otherwise R might take a while to find them. Your raster is quite large so this might all take a while anyway.

  • Amazing! You saved me a lot of time - brilliant. Thank you.
    – Thomas
    Sep 23 at 13:31

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