Hi Jim,

Oh wow thanks so much. One question though, did you notice that the
12:00:00 slot is missing entirely from the output? It shows 11:52:30 and
12:07:30, but not 12:00:00. Actually after another review I see that it's
missing the 12, 12:15, and 12:30?

>2012-07-22 11:52:30 2012-07-22 12:07:30 2012-07-22 12:22:30 2012-07-22
12:37:30
>                 NA            22.33333                  NA
 24.00000
>2012-07-22 12:52:30
>           20.00000

Any ideas how to fix this?

Thanks again!
Jason


On Mon, Aug 27, 2012 at 1:40 PM, jim holtman <jholtman@gmail.com> wrote:

> try this:
>
>
> > x <- read.table(text = "2012-07-22 12:12:00, 21
> + 2012-07-22 12:15:00, 22
> + 2012-07-22 12:18:00, 24
> + 2012-07-22 12:39:00, 21
> + 2012-07-22 12:45:00, 25
> + 2012-07-22 12:49:00, 26
> + 2012-07-22 12:53:00, 20
> + 2012-07-22 13:00:00, 18
> + 2012-07-22 13:06:00, 22", colClasses = c("POSIXct", "integer"), sep =
> ',')
> > # get minimum at an hour granularity
> > tMin <- trunc(min(x$V1), units = 'hour')
> > # back off 7.5 minute
> > tMin <- tMin - (7.5 * 60)
> > # create sequence for 'cut'
> > cSeq <- seq(tMin, max(x$V1) + (7.5 * 60), by = '15 min')
> > # now split and average
> > cCut <- cut(x$V1, cSeq)
> > # compute means
> > tapply(x$V2, cCut, mean)
> 2012-07-22 11:52:30 2012-07-22 12:07:30 2012-07-22 12:22:30 2012-07-22
> 12:37:30
>                  NA            22.33333                  NA
>  24.00000
> 2012-07-22 12:52:30
>            20.00000
> >
>
>
> On Mon, Aug 27, 2012 at 9:53 AM, Jason Gilmore <wj@wjgilmore.com> wrote:
> >
> > Hi,
> >
> > I'm pretty new to R and have run into a task which although I'm certain
> is
> > within R's capabilities, falls outside of mine. :-) Consider the
> following
> > data set:
> >
> > 2012-07-22 12:12:00, 21
> > 2012-07-22 12:15:00, 22
> > 2012-07-22 12:18:00, 24
> > 2012-07-22 12:39:00, 21
> > 2012-07-22 12:45:00, 25
> > 2012-07-22 12:49:00, 26
> > 2012-07-22 12:53:00, 20
> > 2012-07-22 13:00:00, 18
> > 2012-07-22 13:06:00, 22
> >
> > My task involves creating a data set which *averages* these values at a
> > resolution of 15 minutes, meaning that I need to average the values
> falling
> > within 7.5 minutes of a 15 minute increment. Therefore given the above
> data
> > set I need to treat it as three groups:
> >
> > 2012-07-22 12:12:00, 21
> > 2012-07-22 12:15:00, 22
> > 2012-07-22 12:18:00, 24
> >
> > 2012-07-22 12:39:00, 21
> > 2012-07-22 12:45:00, 25
> > 2012-07-22 12:49:00, 26
> >
> > 2012-07-22 12:53:00, 20
> > 2012-07-22 13:00:00, 18
> > 2012-07-22 13:06:00, 22
> >
> > The end result should look like this:
> >
> > 2012-07-22 12:15:00, 22.33
> > 2012-07-22 12:30:00, NA <- Because this 15 minute slot did not previously
> > exist
> > 2012-07-22 12:45:00, 24
> > 2012-07-22 1:00:00, 20
> >
> > Any help much appreciated. I've been working on this for several hours
> with
> > little success. I'm able to identify the missing (NA) value using zoo/xts
> > but can't seem to sort out the averaging matter.
> >
> > Thanks so much!
> > Jason
> >
> >         [[alternative HTML version deleted]]
> >
> > ______________________________________________
> > R-help@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.
>

	[[alternative HTML version deleted]]


