code: public int[] getTrace (String base) throws CompoundNotFoundException {
  		if (base.equals("A")) {
  			return A;
  		} else if (base.equals("C")) {
  			return C;
  		} else if (base.equals("G")) {
  			return G;
  		} else if (base.equals("T")) {
  			return T;
  		} else {
  			throw new CompoundNotFoundException("Don't know base: " + base);
  		}
  	}
docs: Returns one of the four traces - all of the y-coordinate values,
  each of which correspond to a single x-coordinate relative to the
  position in the array, so that if element 4 in the array is 972, then
  x is 4 and y is 972 for that point.
  
  @param base - the DNA String to retrieve the trace values for
  @return an array of ints giving the entire trace for that base
  @throws CompoundNotFoundException if the base is not valid