It depends on if the person wants to change. You also didn't specify whether this change was for the good or not. It's easy for people to change for the worst if influenced by others. My dad always used to say that one bad apple spoils the bunch. Typically this doesn't work the other way around, you can't wipe a clean surface with a dirty rag and expect the rag to come away clean as well as the spot you touched; both will simply be dirty. However, someone can decide that they're tired of being the "bad guy" and change themselves from within, but this is a journey of self-purging and one must distance thenselves from any bad influences.
Once someone has started down such a recovery, they may pursue better people to associate with, but must be careful not to contaminate them and just let their good influence slowly seep in over time...it doesn't happen overnight and most of the changing is done by the person, not their friends.