[R] subsetting time series

[David Winsemius]

On Dec 13, 2012, at 8:52 AM, m p wrote:

> Hello,
> my series of dates look like
>
>  [1] "2012-05-30 18:30:00 UTC" "2012-05-30 19:30:00 UTC"
>  [3] "2012-05-30 20:30:00 UTC" "2012-05-30 21:30:00 UTC"
>  [5] "2012-05-30 22:30:00 UTC" "2012-05-30 23:30:00 UTC"
>  [7] "2012-05-31 00:30:00 UTC" "2012-05-31 01:30:00 UTC"
>  [9] "2012-05-31 02:30:00 UTC" "2012-05-31 00:30:00 UTC"
> [11] "2012-05-31 01:30:00 UTC" "2012-05-31 02:30:00 UTC"
> [13] "2012-05-31 03:30:00 UTC" "2012-05-31 04:30:00 UTC"
> [15] "2012-05-31 05:30:00 UTC" "2012-05-31 06:30:00 UTC"
> [17] "2012-05-31 07:30:00 UTC" "2012-05-31 08:30:00 UTC"
> [19] "2012-05-31 06:30:00 UTC" "2012-05-31 07:30:00 UTC"
> ...
>

Better would have been
  series <- seq(as.POSIXct("2012-05-30 18:30:00", tz= "UTC"),  
length=40, by="1 hour")

> I'd like to subset this to four series

Although you latter describe the problem differently, so I am  
following that description. See if this split approach with modulo  
arithmetic is helpful:

split(series, (0:length(series)-1) %/% 9 )

-- 
David.
>
> 1)
>  [1] "2012-05-30 18:30:00 UTC" "2012-05-30 19:30:00 UTC"
>  [3] "2012-05-30 20:30:00 UTC" "2012-05-30 21:30:00 UTC"
>  [5] "2012-05-30 22:30:00 UTC" "2012-05-30 23:30:00 UTC"
>  [7] "2012-05-31 00:30:00 UTC" "2012-05-31 01:30:00 UTC"
>  [9] "2012-05-31 02:30:00 UTC"
>
> [10] "2012-05-31 18:30:00 UTC" "2012-05-31 19:30:00 UTC"
> ...
>
> 2)
>                                                "2012-05-31 00:30:00  
> UTC"
> -> [1]
> [11] "2012-05-31 01:30:00 UTC" "2012-05-31 02:30:00 UTC" -> [2,3]
> [13] "2012-05-31 03:30:00 UTC" "2012-05-31 04:30:00 UTC"
> [15] "2012-05-31 05:30:00 UTC" "2012-05-31 06:30:00 UTC"
> [17] "2012-05-31 07:30:00 UTC" "2012-05-31 08:30:00 UTC"
>
> [10] "2012-06-01 00:30:00 UTC"
>
>
> 3)
> [19] "2012-05-31 06:30:00 UTC" "2012-05-31 07:30:00 UTC"
> ...
>
> so that I can plot data for each of the series separately without  
> e.g. data
> at hour  "2012-05-31 02:30:00 UTC"  connecting in the figure to  
> "2012-05-31
> 00:30:00 UTC"
>
> Basically, cycling through the series with period 9
>
> Thanks for any suggestions/help,
> thanks,
>
> Mark
>
> 	[[alternative HTML version deleted]]
>
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David Winsemius, MD
Alameda, CA, USA