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

[Cren]

Thank you for your help, Michael.

I used *aggregate(x, by = timeSequence(by = "day"), FUN = sum)* but the
results is very different from *sum(x[1:13])*, where 13 is the number of
daily observations I've sampled.

Michael Weylandt wrote
> 
> 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@> 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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>>
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> 
> ______________________________________________
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> 


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