public int[] pu_and_py(){
		//count the purines ans the pyrimidines
		int[] count = new int[2]; //purines, pyrimidines
		for (int i=0; i<DNA_analyse.w.raw.length(); ++i){
			switch (DNA_analyse.w.raw.charAt(i)){
			case 'a': case 'A': case 'g': case 'G':
				++count[0];
				break;
			case 'c': case 'C': case 't': case 'T':
				++count[1];
				break;
			}
		}
		return count;
	}