[R] Removing rows with earlier dates
Greg.Snow at imail.org
Sat Dec 25 05:40:07 CET 2010
Whenever a task calls for breaking a data object into pieces, operate on the pieces, then put it back together, then think about using the plyr package.
Sent from my iPod
On Dec 24, 2010, at 6:58 AM, "Ali Salekfard" <salekfard at googlemail.com> wrote:
> Hi all,
> I'm new to the list but have benfited from it quite extensively. Straight to
> my rather strange question:
> I have a data frame that contains mapping rules in this way:
> ACCOUNT, RULE COLUMNS, Effective Date
> The dataframe comes from a database that stores all dates. What I would like
> to do is to create a data frame with only the most recent rule for each
> account. In traditional programming languages I would loop through each
> account find the most recent rule(s) and fill up my updated data frame.
> Does anyone have any better idea to use R's magic (Its syntax is still
> magical to me) for this problem?
> By the way the list of rules is quite extensive (144643 lines to be
> precise), and there are usually 1-3 most recent rules (rows) for each
> [[alternative HTML version deleted]]
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