[R] How to preserve date format while aggregating

[jim holtman]

Try changing the 'class' of the numeric result back to Date:

> x <- as.Date('2008-09-08')
> x
[1] "2008-09-08"
> y <- as.numeric(x)
> y
[1] 14130
> str(y)
 num 14130
> class(y) <- "Date"
> y
[1] "2008-09-08"
> str(y)
Class 'Date'  num 14130
>


On Mon, Sep 8, 2008 at 6:38 AM, Erich Studerus
<erich.studerus at bli.uzh.ch> wrote:
> Hi
>
> I have a dataframe in which some subjects appear in more than one row. I
> want to extract the subject-rows which have the minimum date per subject. I
> tried the following aggregate function.
>
> attach(dataframe.xy)
>
> aggregate(Date,list(SubjectID),min)
>
> Unfortunately, the format of the Date-column changes to numeric, when I'm
> applying this function. How can I preserve the date format?
>
> Thanks
>
> Erich
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>



-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

What is the problem that you are trying to solve?