code: private double link(double d1, double d2) {
  		if (isScoreMatrix) {
  			return Math.max(d1,d2);
  		} else {
  			return Math.min(d1,d2);
  		}
  	}
docs: The linkage function: minimum of the 2 distances (i.e. single linkage clustering)
  @param d1
  @param d2
  @return