public ArrayList<String> avgColumns(int[] c)
	{
		ArrayList<String> results = new ArrayList<String>();

		//for each column we need the average for
		for(int index : c)
		{
			//get the average for an individual column
			String result = avgColumn(index);

			//if the result is valid
			if (!result.contains("NaN") && !result.contains(""))
			{
				//add it to the results array list
				results.add(result);
			}
		}

		return results;
	}