[R] How to sum and group data by DATE in data frame

[R. Michael Weylandt]

How are you using aggregate()? It seems to sum for me...

z <- zoo(1:50, seq.POSIXt(from = Sys.time(), by = "30 min", length.out = 50))

aggregate(z, as.Date(time(z)), sum)

Best,
Michael

On Tue, May 15, 2012 at 11:52 AM, Cren <oscar.soppelsa at bancaakros.it> wrote:
> Hello,
>
> I have a time series with intraday datas, sampled every 30'; I would need to
> aggregate them in this way: summing up all datas within a day.
>
> I tried to use *aggregate(...)* function to get my goal, but it aggregates
> in wrong way (I did not understand how so far); what I need is like
> *sum(...)* function applied to datas within the same day.
>
> Thank you :)
>
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