public static void createStDevGraphFile(int n, int k, String... files)
	{
		try
		{
			int line_number=0;
			
			if(n==2)
				line_number = Ngrams2_lineNumber;
			else if(n==3)
				line_number = Ngrams3_lineNumber;
			else if(n==4)
				line_number = Ngrams4_lineNumber;
			else if(n==5)
				line_number = Ngrams5_lineNumber;
			
			if(files.length == 0)
				return;
			
			String fileout = "output/out1.txt";
			PrintWriter file_writer = new PrintWriter(fileout, "UTF-8");
			file_writer.printf("##|##\n");
			file_writer.printf("Freq|Freq-std|Freq+std\n");
			double stdDev[][];
			
			ArrayList<Ngrams> main;
			//ArrayList<ArrayList<Ngrams>> pool = new ArrayList<ArrayList<Ngrams>>();
			ArrayList<Ngrams>[] pool = (ArrayList<Ngrams>[])new ArrayList[files.length-1];
			ArrayList<Ngrams> aux;
			
			main = getFreqFromDBFile(n, files[0]);
			for(int i=1; i<files.length; i++)
			{
				aux = getFreqFromDBFile(n, files[i]);
				pool[i-1] = aux;
			}
			
			stdDev = getStdDev(line_number, k, pool);
			
			for(int i=0; i<line_number; i++)
			{
				file_writer.printf(" %.8f  | %.8f  | %.8f\n", main.get(i).freq, stdDev[i][0], stdDev[i][1]);
			}
			file_writer.close();
		}
		catch(Exception e)
		{
			System.out.println(e);
		}
	}