{"action":"opened","issue":{"url":"https://api.github.com/repos/CamDavidsonPilon/lifelines/issues/155","labels_url":"https://api.github.com/repos/CamDavidsonPilon/lifelines/issues/155/labels{/name}","comments_url":"https://api.github.com/repos/CamDavidsonPilon/lifelines/issues/155/comments","events_url":"https://api.github.com/repos/CamDavidsonPilon/lifelines/issues/155/events","html_url":"https://github.com/CamDavidsonPilon/lifelines/issues/155","id":79223837,"number":155,"title":"[Question] In _additive_f, why use log instead of directly use division?","user":{"login":"yichuan1118","id":957901,"avatar_url":"https://avatars.githubusercontent.com/u/957901?v=3","gravatar_id":"","url":"https://api.github.com/users/yichuan1118","html_url":"https://github.com/yichuan1118","followers_url":"https://api.github.com/users/yichuan1118/followers","following_url":"https://api.github.com/users/yichuan1118/following{/other_user}","gists_url":"https://api.github.com/users/yichuan1118/gists{/gist_id}","starred_url":"https://api.github.com/users/yichuan1118/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/yichuan1118/subscriptions","organizations_url":"https://api.github.com/users/yichuan1118/orgs","repos_url":"https://api.github.com/users/yichuan1118/repos","events_url":"https://api.github.com/users/yichuan1118/events{/privacy}","received_events_url":"https://api.github.com/users/yichuan1118/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-05-22T00:49:05Z","updated_at":"2015-05-22T00:49:05Z","closed_at":null,"body":"`_additive_f` returns `np.log(population - deaths) - np.log(population)` and `_additive_estimate` `cumsum` in used to get the total. Since numpy do have `cumprod` function, why everything is calculated in log? to avoid overflow?"}}