Combine multilayered_raster vtr using terra package

combine_multylayered_raster_vtr.R

# combine_multylayered_raster_vtr.R: Combine multilayered_raster vtr using terra package
library(terra)

test <- TRUE
test_create_vrt_from_multilayers <- function() {
    raster_objects <- create_multiplayered_rasters()
    print(class(raster_objects[[1]]) == "SpatRaster")
    print(class(raster_objects[[2]]) == "SpatRaster")
    out <- create_vrt_from_multilayers(raster_objects)
    print(out)
    invisible(NULL)
}

create_multiplayered_rasters <- function() {
    A <- rast( nrows=10, ncols=10, xmin=0, xmax=10 )
    B <- rast( nrows=10, ncols=10, xmin=0, xmax=10 )
    C <- rast( nrows=10, ncols=10, xmin=0, xmax=10 )
    values(A) <- 1:100
    values(B) <- 0:99
    values(C) <- rep(0,100)
    raster1 <- rast(list(A,B,C))
    D <- rast( nrows=10, ncols=10, xmin=0, xmax=10 )
    E <- rast( nrows=10, ncols=10, xmin=0, xmax=10 )
    values(D) <- 101:200
    values(E) <- 100:199
    raster2 <- rast(list(D,E))
    return(list(raster1, raster2))
}

create_vrt_from_multilayers <- function(
        raster_objects, 
        output_directory = "rasters", 
        output_vrt_file = "rasters/stacked_rasters.vrt") {
    layer_files <- save_raster_layers_files(raster_objects, output_directory)
    layer_list <- lapply(layer_files, rast)
    raster_stack <- rast(layer_list)
    raster_file <- save_raster_file(raster_stack)
    raster_vrt <- vrt(raster_file, filename = output_vrt_file, overwrite = TRUE)
    str(raster_vrt)
    return(raster_vrt)
}

save_raster_layers_files <- function(multilayered_rasters, output_directory) {
    if (!all(sapply(multilayered_rasters, inherits, "SpatRaster"))) {
        stop("Input must be a list of multilayered SpatRaster objects.")
    }
    if (!dir.exists(output_directory)) {
        dir.create(output_directory)
    }
    all_raster_files <- list()
    for (raster_index in 1:length(multilayered_rasters)) {
        raster_obj <- multilayered_rasters[[raster_index]]
        for (i in 1:nlyr(raster_obj)) {
            file_name <- paste0("raster",raster_index, "_layer", i)
            output_file <- file.path(output_directory, paste0(file_name,".tif"))
            writeRaster(raster_obj[[i]], filename = output_file, overwrite = TRUE)
            all_raster_files <- c(all_raster_files, output_file)
        }
    }
    return(all_raster_files)
}

save_raster_file <- function(raster_obj,  output_directory = "rasters", file_name = "raster.tif") {
    if (!dir.exists(output_directory)) {
        dir.create(output_directory)
    }
    output_file <- file.path(output_directory, file_name)
    writeRaster(raster_obj, filename = output_file, overwrite = TRUE)
    return(output_file)
}

if (test && interactive()){
    test_create_vrt_from_multilayers()
}

Results here: https://gist.github.com/jrosell/c07d8c2d979f1d17a435efb75788012a