code: public ArrayList<String> getDiscreteColumnValues(String column) throws Exception {
  		HashMap<String, String> hashMapValues = new HashMap<String, String>();
  		ArrayList<String> values = new ArrayList<String>();
  		ArrayList<String> rows = getDataRows();
  		for (String row : rows) {
  			String value = getCell(row, column);
  			if (!hashMapValues.containsKey(value)) {
  				hashMapValues.put(value, value);
  				values.add(value);
  			}
  		}
  		return values;
  	}
docs: Get back a list of unique values in the column
  
  @param column
  @return
  @throws Exception