Hi:

On Wed, Aug 18, 2010 at 4:43 PM, skan <juanpide@gmail.com> wrote:

>
> Hi
>
>
> Usually "aggregate" is used to calculate things such as the sum of all data
> on the first day, the sum next day, and so on.
> But how can I calculate the mean of the first hour of all days, the mean of
> the second hour of all days, and so on.  ???
>
> That's
> Most examples:
> today at 1am + today at 2am + today at 3am +....                    -> sum
> today
> tomorrow at 1am + tomorrow at 2am + tomorrow at 3am +....     -> sum
> tomorrow
> ..................
> aggregate(data, as.Date,sum)
>
>
> But what I need is:
> data today at 1 + data tomorrow at 1 + data in two days at 1 + .....    ->
> sum at 1am
> data today at 2 + data tomorrow at 2 + data in two days at 2 + .....    ->
> sum at 2am
> data today at 3 + data tomorrow at 3 + data in two days at 3 + .....    ->
> sum at 3am
> .............
>
> How can I do it??
>

Aggregate by day/hour combinations, put the results in a matrix with days as
rows and hours as columns, and then use colSums(), perhaps?

HTH,
Dennis

>
> cheers
> --
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