[R] time series problem: time points don't match

[Gabor Grothendieck]

On Thu, Apr 1, 2010 at 7:08 PM, Gabor Grothendieck
<ggrothendieck at gmail.com> wrote:
> Perhaps something like this:
>
> library(zoo)
> library(chron)
> # read in data
>
> Lines1 <- "date            time            level           temp
> 2009/10/01 00:01:52.0      2.8797      18.401
> 2009/10/01 00:16:52.0      2.8769      18.382
> 2009/10/01 00:31:52.0      2.8708      18.309
> 2009/10/01 00:46:52.0      2.8728      18.285
> 2009/10/01 01:01:52.0      2.8716      18.245
> 2009/10/01 01:16:52.0      2.8710      18.190"
>
> Lines2 <- "date            time            level          temp
> 2009/10/01 00:11:06.0      2.9507      18.673
> 2009/10/01 00:26:06.0      2.9473      18.630
> 2009/10/01 00:41:06.0      2.9470      18.593
> 2009/10/01 00:56:06.0      2.9471      18.562
> 2009/10/01 01:11:06.0      2.9451      18.518
> 2009/10/01 01:26:06.0      2.9471      18.480"
>
> DF1 <- read.table(textConnection(Lines1), header = TRUE, as.is = TRUE)
> DF2 <- read.table(textConnection(Lines2), header = TRUE, as.is = TRUE)
>
> z1 <- zoo(DF1[3:4], chron(DF1[,1], DF1[,2], format=c("Y/M/D", "H:M:S")))
> z2 <- zoo(DF2[3:4], chron(DF2[,1], DF2[,2], format=c("Y/M/D", "H:M:S")))
>
> # process inputs z1 and z2
> # aggregating into 15 minute intervals and merging
>
> z1a <- aggregate(z1, trunc(time(z1), "00:15:00"), tail, n = 1)
> z2a <- aggregate(z2, trunc(time(z2), "00:25:00"), tail, n = 1)

The last line should have been:

z2a <- aggregate(z2, trunc(time(z2), "00:15:00"), tail, n = 1)

>
> z <- merge(z1a, z2a)
>
>
> On Thu, Apr 1, 2010 at 1:35 PM, Brad Patrick Schneid <bpschn01 at gmail.com> wrote:
>>
>> Hi,
>> I have a time series problem that I would like some help with if you have
>> the time.  I have many data from many sites that look like this:
>>
>> Site.1
>> date            time            level           temp
>> 2009/10/01 00:01:52.0      2.8797      18.401
>> 2009/10/01 00:16:52.0      2.8769      18.382
>> 2009/10/01 00:31:52.0      2.8708      18.309
>> 2009/10/01 00:46:52.0      2.8728      18.285
>> 2009/10/01 01:01:52.0      2.8716      18.245
>> 2009/10/01 01:16:52.0      2.8710      18.190
>>
>> Site.2
>> date            time            level          temp
>> 2009/10/01 00:11:06.0      2.9507      18.673
>> 2009/10/01 00:26:06.0      2.9473      18.630
>> 2009/10/01 00:41:06.0      2.9470      18.593
>> 2009/10/01 00:56:06.0      2.9471      18.562
>> 2009/10/01 01:11:06.0      2.9451      18.518
>> 2009/10/01 01:26:06.0      2.9471      18.480
>>
>> As you can see, the times do not match up.  What I would like to do is be
>> able to merge these two data sets to the nearest time stamp by creating a
>> new time between the two; something like this:
>>
>>
>> date            new.time        level.1       temp.1    level.2         temp.2
>> 2009/10/01 00:01:52.0      2.8797      18.401   NA             NA
>> 2009/10/01 00:13:59.0      2.8769      18.382      2.9507      18.673
>> 2009/10/01 00:28:59.0      2.8708      18.309      2.9473      18.630
>> 2009/10/01 00:43:59.0      2.8728      18.285      2.9470      18.593
>> 2009/10/01 00:59:59.0      2.8716      18.245     2.9471      18.562
>> 2009/10/01 01:13:59.0      2.8710      18.190     2.9451      18.518
>> 2009/10/01 01:26:06.0       NA              NA          2.9471      18.480
>>
>> Note that the sites may not match in the # of observations and a return of
>> NA would be necessary, but a deletion of that time point all together for
>> both sites would be preferred.
>>
>> A possibly easier alternative would be a way to assign generic times for
>> each observation according to the time interval, so that the 1st observation
>> for each day would have a time = 00:00:00 and each consecutive one would be
>> 15 minutes later.
>>
>> Thanks for any suggestions.
>>
>> Brad
>>
>> --
>> View this message in context: http://n4.nabble.com/time-series-problem-time-points-don-t-match-tp1748387p1748387.html
>> Sent from the R help mailing list archive at Nabble.com.
>>
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>>
>