R error in .calcTest for larger .tif files

Question

I have 175 tif files including gridded data for various crops for the whole globe (land). I want to create a single raster data set that only contains the index of the highest value. So that for each cell I know which crop has the highest value.

My code works. But if I run the calc() function I sometimes get an error that I cannot explain:

Error in .calcTest(x[1:5], fun, na.rm, forcefun, forceapply) : cannot use this function. Perhaps add '...' or 'na.rm' to the function arguments?

library(raster)
# Get the file names for later import
file_list <- list.files(path = "C:/folder/test", full.names = TRUE)
filtered_file_list <- file_list[grep("HarvestedAreaFraction.tif",file_list,fixed=TRUE)]

#init
raster_stack <- stack()
crop_names <- character() #list to save the index of crops


for (file_path in filtered_file_list){
  raster_layer <- raster(file_path)
  
  # Aggregate the raster to a 1-degree resolution, all tif-files have the same resolution
  aggregated_raster_layer <- aggregate(raster_layer, fact=c(12,12), fun=mean) 
  raster_layer <- na.omit(aggregated_raster_layer)
  
  raster_stack <- addLayer(raster_stack, raster_layer)
  crop_name <- gsub(".*/(.*?)_HarvestedAreaFraction\\.tif$", "\\1", file_path)
  crop_names <- c(crop_names, crop_name)
}

# Function to get the name of the crop with the maximum fraction
get_max_crop_name <- function(x, na.rm = TRUE, ...) {
  max_index <- which.max(x)
#  max_name <- crop_names[max_index]
  if (length(max_index) == 0 || all(x == 0) || all(is.na(x))) {
    max_name <- 0
  } else {
    max_name <- max_index
  }
  return(max_name)
}

max_crop_raster <- calc(raster_stack, fun=get_max_crop_name, na.rm=TRUE)

The error only occurs when I import the larger tif-files. Out of the 175 files about 100 are about 30MB and the other are about 2-3MB. It works fine for the smaller ones but as soon as I include one of the larger ones I get this error

Any ideas?

Answer 1

The reason this does not work is that your function is not vectorized, because if statements can only evaluate one value at a time.
You do not need any of this anyway, as you can use wich.max. like this (with "terra", the replacement for "raster"):

library(terra)
ff <- list.files(path = "C:/folder/test", full.names = TRUE, pattern="HarvestedAreaFraction.tif")

x <- rast(ff)
mxcrop <- which.max(x)