file_builder <- function(file_n=12,
                         file_folder="RandomFiles/",
                         file_size=c(15,100),
                         file_na=3){
  for (i in seq_len(file_n)) {
    file_length <- sample(file_size[1]:file_size[2],size=1) # get number of rows
    var_x <- runif(file_length) # create random x
    var_y <- runif(file_length) # create random y
    df <- data.frame(var_x,var_y) # bind into a data frame
    bad_vals <- dpois(x=1,lambda=file_na, log=FALSE) # determine NA number
    df[sample(nrow(df),size=bad_vals),1] <- NA # random NA in var_x
    df[sample(nrow(df),size=bad_vals),2] <- NA # random NA in var_y
    
    # create label for file name with padded zeroes
    file_label <- paste(file_folder,
                        "ranFile",
                        formatC(i,
                                width=3,
                                format="d",
                                flag=0),
                        ".csv",sep="")
    
    # set up data file and incorporate time stamp and minimal metadata
    write.table(cat("# Simulated random data file for batch processing","\n",
                    "# timestamp: ",as.character(Sys.time()),"\n",
                    "# JAH","\n",
                    "# ------------------------", "\n",
                    "\n",
                    file=file_label,
                    row.names="",
                    col.names="",
                    sep=""))
    
    # now add the data frame
    write.table(x=df,
                file=file_label,
                sep=",",
                row.names=FALSE,
                append=TRUE)
    
    
  } # end loop
} # end file_builder

file_builder()
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file
## ""
## Warning in write.table(x = df, file = file_label, sep = ",", row.names =
## FALSE, : appending column names to file