Extracting digits, upper lower letter from a string using TR

[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss5" | tr -cd '[[:upper:]]\n'
VIKAS
[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss5" | tr -cd '[[:lower:]]\n'
vikas
[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss5" | tr -cd '[[:digit:]]\n'
12345
[root@vikas ~]# echo "Vv1Ii2Kk 3Aa4Ss5" | tr -cd '[[:blank:]]\n'

[root@vikas ~]# echo "Vv1Ii2Kk3Aa4Ss$$5" | tr -cd '[[:alpha:]]\n'
VvIiKkAaSs
[root@vikas ~]#