Thanks for the inputs, but it's not exactly what I want...

My problem is, that my timeseries (precipitation) contain lots of NA-values

and when I apply the code:

z<- data.frame(a=p1$time.date, precip=p1$m1)
#gives a dataframe with precipitation and time (2004-01-01 02:12:00)
z<- z[complete.cases(z),]
m1.h<-tapply(z$precip, as.POSIXct(trunc(z$a, 'day')), sum)
#gives me the daily sum values of this serie (I need to redo this also for
hourly values)
m1.h<-as.data.frame(m1.h)

to get daily summations, the NAs are out and the time series is not
continous, therefore I need the time/dates corresponding to the measurement
back in the DATA-FRAME!

Can I do this, or is the way with tapply/trunc wrong to get hourly/daily
summation of my measurements (which are originally in 10 and 15 min period
(randomly).

really, really thanks a lot...

Marc

2007/8/23, Achim Zeileis <Achim.Zeileis@wu-wien.ac.at>:
>
> On Thu, 23 Aug 2007 mgilgen@swissonline.ch wrote:
>
> > i'm trying to convert a zoo object of the following specifications:
> >
> > > str(z)
> >  atomic [1:15642] 0 0 0 0 0 0 0 0 0 0 ...
> >  - attr(*, "index")='POSIXct', format: chr [1:15642] "2004-09-01
> 02:00:00" "2004-09-01 03:00:00" "2004-09-01 04:00:00" "2004-09-01 05:00:00"
> ...
> >  - attr(*, "frequency")= num 0.000278
>
> (Side note 1: The frequency looks suspicious...you probably want a "zoo"
> rather than a "zooreg" object.)
>
> > to convert into a dataframe. the atomic object (or what it is...) is
>
> (Side note 2: a vector for univariate zoo series, a matrix for
> multivariate zoo series.)
>
> > convertet correctly, but the time attribute in the POSIXct format is
> > replaced by an index number
> >
> > how can i get my data with the corresponding date/time as a second
> column?
>
> Just add it afterwards, e.g.,
>   z <- zoo(cbind(a = 1:5, b = 2:6), as.POSIXct(as.Date("2007-01-01") +
> 0:4))
>   d <- as.data.frame(z)
>   d$Date <- time(z)
>
> (Side note 3: The reason for not including the date is that we wanted the
> data to be as similar as possible in the zoo series and the data frame,
> e.g., for
>   lm(a ~ ., data = as.data.frame(z))
> )
>
> hth,
> Z
>
>
>


-- 
***
Marc Gilgen
Plattenstrasse 21
8032 Zürich
+41 78 686 06 49
marc.gilgen@gmail.com

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