Question

How to select optimal epsilon value in dbscan algorithm?

Answer 1

I believe this discussion will be of help to you:

http://stackoverflow.com/questions/12893492/choosing-eps-and-minpts-for-dbscan-r

ARCADE allows for all EPS values using DBSCAN without knowing a priori density estimates:

http://nebula.wsimg.com/b573f6daeaad3f38ead59a00eae13ffd?AccessKeyId=BDCFD2864AC62650B045&disposition=0&alloworigin=1