{"action":"opened","issue":{"url":"https://api.github.com/repos/Rdatatable/data.table/issues/1313","labels_url":"https://api.github.com/repos/Rdatatable/data.table/issues/1313/labels{/name}","comments_url":"https://api.github.com/repos/Rdatatable/data.table/issues/1313/comments","events_url":"https://api.github.com/repos/Rdatatable/data.table/issues/1313/events","html_url":"https://github.com/Rdatatable/data.table/issues/1313","id":105039929,"number":1313,"title":"invisible with hist does not suppress output","user":{"login":"trinker","id":1763278,"avatar_url":"https://avatars.githubusercontent.com/u/1763278?v=3","gravatar_id":"","url":"https://api.github.com/users/trinker","html_url":"https://github.com/trinker","followers_url":"https://api.github.com/users/trinker/followers","following_url":"https://api.github.com/users/trinker/following{/other_user}","gists_url":"https://api.github.com/users/trinker/gists{/gist_id}","starred_url":"https://api.github.com/users/trinker/starred{/owner}{/repo}","subscriptions_url":"https://api.github.com/users/trinker/subscriptions","organizations_url":"https://api.github.com/users/trinker/orgs","repos_url":"https://api.github.com/users/trinker/repos","events_url":"https://api.github.com/users/trinker/events{/privacy}","received_events_url":"https://api.github.com/users/trinker/received_events","type":"User","site_admin":false},"labels":[],"state":"open","locked":false,"assignee":null,"milestone":null,"comments":0,"created_at":"2015-09-05T17:49:38Z","updated_at":"2015-09-05T17:49:38Z","closed_at":null,"body":"I am using version 1.9.5 of data table and read in the FAQ:\r\n\r\n> 2.18 I’m using j for its side effect only, but I’m still getting data returned. How do I stop that?\r\n> In this case j can be wrapped with `invisible()`; e.g., `DT[,invisible(hist(colB)),by=colA]`\r\n\r\nBut using the code below the output is still printed and I get the warning that I on't quiet understand seen at the end of the post.\r\n```r\r\nlibrary(data.table)\r\nDT <- data.table(colA=rep(1:5,each=3), colB=floor(runif(15)*10))\r\nDT[,invisible(hist(colB)),by=colA]\r\n```\r\n\r\n```\r\nWarning message:\r\nIn `[.data.table`(DT, , invisible(hist(colB)), by = colA) :\r\n  Column 2 of result for group 1 is length 5 but the longest column in this result is 6. Recycled leaving remainder of 1 items. This warning is once only for the first group with this issue.\r\n```"}}