Need help regarding hook_votingapi_results_alter

Hello,

previously i was using with drupal 5 hook_votingapi_calculate() but now i need to replace this with hook_votingapi_results_alter() as suggested in api.txt

i was doing it this way.

$previous = get_data($content_id);
$cache['karma']['karma_points']['sum'] = $previous;

i found something diff with the example. if i use this same code with the hook_votingapi_results_alter() , is there anything which i am missing or doing wrong??

Thanks,
sweetie