Naming raster layers in a rasterstack with the same name

Question

I have a for loop where I loop layers from a rasterstack into a predict function, which requires the output of a model and two raster files, including one layer for the present ("rastFile") and one stack or brick for the future ("stackedRast"), as follows:

  for (i in 1:94){
  
  timePred <- predict(G15.gdm.1, rastFile, time=TRUE, predRasts=stackedRast[[i]])
  
  stack(timePred,stackedRast[[i]])
  
  writeRaster(timePred, "xxxxx.tif")
  
  rm(timePred)
  
}

First of all, for the predict function to work, I need all the layers in the rasterstack to have the same name, for instance "bio1"

for (i in 1:nlayers(stacked)) {names(stacked[[i]]) <- "bio1"}

However, R adds a number to the end of the layer names, like this:

> stackedRast
class      : RasterStack 
dimensions : 1200, 2760, 3312000, 4  (nrow, ncol, ncell, nlayers)
resolution : 0.04166667, 0.04166667  (x, y)
extent     : -180, -65, 35, 85  (xmin, xmax, ymin, ymax)
crs        : +proj=longlat +datum=WGS84 +no_defs +ellps=WGS84 +towgs84=0,0,0 
names      :    bio1.1,    bio1.2,    bio1.3,    bio1.4 
min values : -24.70417, -22.44583, -19.79583, -16.23750 
max values :  25.96667,  27.47917,  28.76250,  30.28750 

Is there a way to get around this? (P.S. I've just included a smaller rasterstack of 4 layers for the example, but my final rasterstack will have 94 layers).

Does anyone please have a suggestion for how I can elegantly create one process (loop or otherwise) for changing the layer names so that they all match?

Answer 1

The raster package is very strict about names, it seems, and really doesn't want you to have two layers in a stack with the same names. Weirdly you can make a plain R list with two elements with the same name:

> L = list(a=1, a=2)
> L$a
[1] 1
> names(L)
[1] "a" "a"

but the only way to get the second one is with L[[2]].

But the raster package goes through a lot of effort to stopping you from doing this.

I think you'll have to pull each layer out and name it individually as you go through the loop. For example:

for (i in 1:94){
  stackedRast_i = stackedRast[[i]]
  names(stackedRast_i) = "bio1"
  timePred <- predict(G15.gdm.1, rastFile, time=TRUE,
    predRasts=stackedRast_i)
  ...

There's a neater way of doing this via setNames which returns a named version of its argument:

> s1 = setNames(s[[1]], "bio1")
> names(s1)
[1] "bio1"

So your loop can be:

 for (i in 1:94){
    timePred <- predict(G15.gdm.1, rastFile, time=TRUE,
      predRasts=setNames(stackedRast[[i]],"bio1"))

Note this doesn't change the names of stackedRast, it returns a raster layer with the name set on it.