public static float[][] randomEntry(float[][]originalMatrix, double rate) {
		
		int userNumber = originalMatrix.length;
		int serviceNumber = originalMatrix[0].length;
		float[][] randomedMatrix = new float[userNumber][serviceNumber];
		float range = getMaxValue(originalMatrix);
		
		copyMatrix(originalMatrix, randomedMatrix);
		int randomUserNumber = (int)(userNumber * rate);
		ArrayList<Integer> list = new ArrayList<Integer>();
		int index;
		Random random = new Random(System. currentTimeMillis());
		for (int i = 0; i < randomUserNumber; i++) {
			do {
				index = random.nextInt(userNumber);
			} while(list.contains(new Integer(index)));
			list.add(new Integer(index));	
			for(int j = 0; j < originalMatrix[0].length; j++){
				if (originalMatrix[index][j] != -1 && originalMatrix[index][j] != -2) {
					randomedMatrix[index][j] = range * random.nextFloat();
				}				
			}
		}
		writeFile("unreliableUsers.txt", list.toString());
		return randomedMatrix;
	}