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Aggregate dataframe variables, return more than 2 vars
2 messages · violet lock, Martin Maechler
Not at all appropriate to be posted to R-devel :
"vl" == violet lock <violetlock at gmail.com>
on Tue, 9 Feb 2010 17:00:48 -0500 writes:
> Hello r-devel,
> I have data.frame with 3 columns and I would like to group by 1 column(id),
> find the max of the third column (date) and return the data for that max
> date value along with the id and the value in the second column.
> Example:
>> dat <- data.frame(id = rep(1:3, 3), date = as.Date(rep(c("2005-08-25",
> "2005-08-26", "2005-08-29"), each = 3)), decod = c("SCREEN", "SCREEN",
> "SCREEN", "RAND", "RAND", "RAND", "COMPLETE", "COMPLETE", "WITHDRAWAL") )
> What I need is it to return is:
[...............]
[...............]
> Any ideas would be appreciated,
E-mails that look like the above *CLEARLY* belong to R-help
and *NEVER* to R-devel.
Please read the posting guide
PLEASE do read the posting guide http://www.R-project.org/posting-guide.html and provide commented, minimal, self-contained, reproducible code.
and *then* repost to R-help! Martin Maechler, ETH Zurich