[R] Grouping miliseconds By Hours

[David Winsemius]

On Feb 5, 2012, at 9:54 AM, jim holtman wrote:

> Is this what you are after:
>
>> x <- c(1327211358, 1327221999, 1327527296, 1327555433, 1327701042,
> + 1327761389, 1327780993, 1327815670, 1327822964, 1327897497,  
> 1327897527,
> + 1327937072, 1327938300, 1327957589, 1328044466, 1328127921,  
> 1328157588,
> + 1328213951, 1328236836, 1328300276, 1328335936, 1328429102)
>>
>> x <- as.POSIXct(x, origin = '1970-1-1')
>> x
> [1] "2012-01-22 05:49:18 EST" "2012-01-22 08:46:39 EST" "2012-01-25
> 21:34:56 EST"
> [4] "2012-01-26 05:23:53 EST" "2012-01-27 21:50:42 EST" "2012-01-28
> 14:36:29 EST"
> [7] "2012-01-28 20:03:13 EST" "2012-01-29 05:41:10 EST" "2012-01-29
> 07:42:44 EST"
> [10] "2012-01-30 04:24:57 EST" "2012-01-30 04:25:27 EST" "2012-01-30
> 15:24:32 EST"
> [13] "2012-01-30 15:45:00 EST" "2012-01-30 21:06:29 EST" "2012-01-31
> 21:14:26 EST"
> [16] "2012-02-01 20:25:21 EST" "2012-02-02 04:39:48 EST" "2012-02-02
> 20:19:11 EST"
> [19] "2012-02-03 02:40:36 EST" "2012-02-03 20:17:56 EST" "2012-02-04
> 06:12:16 EST"
> [22] "2012-02-05 08:05:02 EST"
>> table(format(x, "%H"))
>
> 02 04 05 06 07 08 14 15 20 21
> 1  3  3  1  1  2  1  2  4  4

It's possible that you may not realize that jim holman has implicitly  
given you a handle on doing operations on such groups, since you could  
use the value of format(x. "%H") as the indexing argument in tapply,  
ave, or aggregate.

-- 
David.


>>
>>
>
>
> On Sun, Feb 5, 2012 at 4:54 AM, Hasan Diwan <hasan.diwan at gmail.com>  
> wrote:
>> I have a list of numbers corresponding to timestamps, a sample of  
>> which follows:
>> c(1327211358, 1327221999, 1327527296, 1327555433, 1327701042,
>> 1327761389, 1327780993, 1327815670, 1327822964, 1327897497,  
>> 1327897527,
>> 1327937072, 1327938300, 1327957589, 1328044466, 1328127921,  
>> 1328157588,
>> 1328213951, 1328236836, 1328300276, 1328335936, 1328429102)
>>
>> I would like to group these into hours. In other words, something  
>> like:
>> c( "2012-01-31 21:14:26 PST" "2012-02-01 20:25:21 PST"
>>  "2012-02-02 04:39:48 PST" "2012-02-02 20:19:11 PST"
>> "2012-02-03 02:40:36 PST" "2012-02-03 20:17:56 PST"
>> "2012-02-04 06:12:16 PST" "2012-02-05 08:05:02 PST")
>> Hour  Hits
>> 21      1
>> 20      3
>> 4        1
>> 2        1
>> 6        1
>> 8        1
>>
>> How would I do this without too much pain (from a CPU perspective)?
>> This is a subset of a million entries and I would rather not go
>> through these manually... So, any advice? Many thanks! -- H
>> --
>> Sent from my mobile device
>> Envoyait de mon portable
>>
>> ______________________________________________
>> 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
> Data Munger Guru
>
> What is the problem that you are trying to solve?
> Tell me what you want to do, not how you want to do it.
>
> ______________________________________________
> 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.

David Winsemius, MD
West Hartford, CT