{"action":"opened","issue":{"url":"https://api.github.com/repos/vega/vega-lite/issues/597","labels_url":"https://api.github.com/repos/vega/vega-lite/issues/597/labels{/name}","comments_url":"https://api.github.com/repos/vega/vega-lite/issues/597/comments","events_url":"https://api.github.com/repos/vega/vega-lite/issues/597/events","html_url":"https://github.com/vega/vega-lite/issues/597","id":109757856,"number":597,"title":"Determine how null values should be handled","user":{"login":"kanitw","id":111269,"avatar_url":"https://avatars.githubusercontent.com/u/111269?v=3","gravatar_id":"","url":"https://api.github.com/users/kanitw","html_url":"https://github.com/kanitw","followers_url":"https://api.github.com/users/kanitw/followers","following_url":"https://api.github.com/users/kanitw/following{/other_user}","gists_url":"https://api.github.com/users/kanitw/gists{/gist_id}","starred_url":"https://api.github.com/users/kanitw/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/kanitw/subscriptions","organizations_url":"https://api.github.com/users/kanitw/orgs","repos_url":"https://api.github.com/users/kanitw/repos","events_url":"https://api.github.com/users/kanitw/events{/privacy}","received_events_url":"https://api.github.com/users/kanitw/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-10-05T09:16:07Z","updated_at":"2015-10-05T09:16:07Z","closed_at":null,"body":"Currently Vega-lite automatically adds null filters for fields with quantitative (Q) type and temporal (T) type by default (based on `filterNull` config).  \r\n\r\nHowever, we need some nice mechanism to deal with null value.  \r\nFor example, should null value be always filtered?  \r\n\r\nIf they are not filtered, how should we display them online. "}}