Classification of jpg files into several one letter subfolders

example.r

# example of usage
setwd("c:/Users/simecekp/Downloads/")
fls <- dir(patter=".*jpg")
jpg_sort(fls,c("a", "s")) 

jpg_sort.r

library(keypress)
library(jpeg)

jpg_sort <- function(files, keys, move.files=FALSE) {

  ## checking intputs
  
  # all keys should be of length 1
  stopifnot(nchar(keys)==1)
  # all keys should be unique
  stopifnot(length(keys)==length(unique(keys)))
  # all files should exist
  stopifnot(file.exists(files))
  # number of files > 0
  stopifnot(length(files)>0)
  # number of keys > 1
  stopifnot(length(keys)>1)
  
  ## creating folders
  for (k in keys) {
    if (!dir.exists(k)) dir.create(k)
  }
  
  ## copy or move?
  if (move.files) {
    file.proc <- file.rename
  } else {
    file.proc <- file.copy
  }
  
  for (i in seq_along(files)) {
    f = files[i]
    jpeg <- readJPEG(f, native=TRUE)
    plot(0:1, 0:1, type="n", ann=FALSE, axes=FALSE)
    rasterImage(jpeg,0,0,1,1)
    Sys.sleep(0.1)
    x <- keypress()
    while (!(x %in% keys)) x <- keypress()
    file.proc(f, paste0(x,"/"))
  }  
}

keypress does not work in RStudio, needs to be run in terminal