For looooops

                                                                  X2 = col_number()))
folder <- setwd("C:\\Users\\sonia\\OneDrive\\BioBeats\\resilience and stress\\Resilience and stress study\\data\\RR")


for (f in folder) {

  f <- read_table2(files, col_names = FALSE, col_types = cols(X1 = col_number(),
                                                              X2 = col_number()))
  subj_id <- lapply(str_split(f, '_'),
                    function(x) {str_split(x[1], '-')[[1]][2]})


#fino a qui funziona ma gli devo dire di prendere tutti i file
}

  for (f in files) {
  Df <- as.data.frame(f)
  }

  for (i in subj_id) {
   new_df <- mutate(Df, participant_id = subj_id[i])
  print(new_df)
  }