[R] separate date and time

[Schatzi]

That is wonderful. Thank you.
Adele


Ken Takagi wrote:
> 
> Schatzi <adele_thompson <at> cargill.com> writes:
> 
>> 
>> I have a combined date and time. I would like to separate them out into
>> two
>> columns so I can do things such as take the mean by time across all
>> dates.
>> 
>> meas<-runif(435)
>> nTime<-seq(1303975800, 1304757000, 1800)
>> nDateT<-as.POSIXct(nTime, origin="1970-01-01")
>> mat1<-cbind(nDateT,meas)
>> 
>> means1<- aggregate(mat1$meas, list(nDateT), mean)
>> 
>> This doesn't do anything as each day is different, but if I had just the
>> time, it would take the mean outputing 48 values (for each 30 min).
>> 
>> Also, sometimes there are missing meas to a specific time. Is there
>> anyway
>> to copy the previous meas if one is missing?
>> 
>> -----
>> In theory, practice and theory are the same. In practice, they are not -
> Albert Einstein
>> --
>> View this message in context:
> http://r.789695.n4.nabble.com/separate-date-and-time-tp3517571p3517571.html
>> Sent from the R help mailing list archive at Nabble.com.
>> 
>> 
> 
> Not sure if this is what you want, but you can use substr to split nDateT
> into
> date and time, and then use aggregate() in the time column in df1.
> 
> meas<-runif(435)
> nTime<-seq(1303975800, 1304757000, 1800)
> nDateT<-as.POSIXct(nTime, origin="1970-01-01")
> date <- substr(nDateT, 1, 10)
> time <- substr(nDateT, 12, 19)
> df1 <- data.frame(date, time, meas)
> 
> means1<- aggregate(df1$meas, list(df1$time), mean)
> 
> HTH,
> Ken
> 
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-----
In theory, practice and theory are the same. In practice, they are not - Albert Einstein
--
View this message in context: http://r.789695.n4.nabble.com/separate-date-and-time-tp3517571p3517999.html
Sent from the R help mailing list archive at Nabble.com.