Hi Tom, It has been fixed in 1.9.3, bug#481. You can scroll down the project page on instructions for installation..
Best, Arun From: Tom Harrop <[email protected]> Reply: Tom Harrop <[email protected]>> Date: August 4, 2014 at 1:40:32 PM To: [email protected] <[email protected]>> Subject: [datatable-help] Unexpected behaviour using fast grouping Hello, I'm trying to group a data.table that has duplicate keys, aggregating the values in another column by the value of the key. There is a question and answer on the same topic on StackOverflow (http://stackoverflow.com/a/17033371/3017012), but when I follow the accepted answer I get different results: > library(data.table) data.table 1.9.2 For help type: help("data.table") > dt = data.table(user_id = c(1,2,2,3), advertiser_id = c(1:4)) > dt[,list(list(advertiser_id)), by = user_id] user_id V1 1: 1 4,3 2: 2 4,3 3: 3 4,3 Where I expect: user_id V1 1: 1 1 2: 2 2,3 3: 3 4 I can get the expected results (as above) using: > dt[,paste(advertiser_id, collapse = ","), by = user_id] Have I missed something? I'm on R 3.1.1 in case the behaviour has changed recently. Many thanks, Tom _______________________________________________ datatable-help mailing list [email protected] https://lists.r-forge.r-project.org/cgi-bin/mailman/listinfo/datatable-help
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