[R] Applying Logical statement to DateTime string as factor

[Gabor Grothendieck]

As mentioned, read R News 4/1 and its references for info on
dates and times.

On Tue, Aug 18, 2009 at 5:06 PM, Pat Schmitz<pschmitz at illinois.edu> wrote:
> Fantastic, that works fantastically.  Is there a optimal way to search R
> News topics, so that I can catch references like this? For all my searching
> of list serves, and documentation, I found very little which could help me.
>
> I have however, had excellent help with R-help, Gabor, I appreciate your
> response very much.
>
> Pat
>
> On Tue, Aug 18, 2009 at 5:18 AM, Gabor Grothendieck <ggrothendieck at gmail.com
>> wrote:
>
>> Try this:
>>
>>
>> Lines <- '"1","30 Jun 2009 18:14:59"
>> "2","02 Jul 2009 07:33:37"
>> "3","06 Jul 2009 08:22:35"
>> "4","06 Jul 2009 19:25:50"
>> "5","08 Jul 2009 08:41:48"
>> "6","10 Jul 2009 07:31:39"
>> "7","10 Jul 2009 19:59:25"
>> "8","13 Jul 2009 07:49:18"
>> "9","13 Jul 2009 18:52:52"
>> "10","15 Jul 2009 08:06:56"
>> "11","15 Jul 2009 19:03:01"
>> "12","17 Jul 2009 08:02:02"'
>>
>> library(chron)
>> DF <- read.csv(textConnection(Lines), header = FALSE, as.is = TRUE)
>> dd <- as.chron(DF$V2, "%d %b %Y %H:%M:%S")
>>
>> dd - dates(dd) > times("12:00:00")  # c(TRUE, FALSE, ...)
>>
>>
>> See R News 4/1 and its references for more.
>>
>>
>> On Tue, Aug 18, 2009 at 3:42 AM, Pat Schmitz<pschmitz at illinois.edu> wrote:
>> > R-Help
>> >
>> > I have a data set which uses a DateTime string as follows : "2009-06-30
>> > 18:14:59"
>> > While I have been able to convert to DateTime properly
>> >
>> > time <- strptime(as.character(dat$Time),format='%d %b %Y %T') #Convert to
>> > dateTime string
>> >
>> > I would like to use the time of day "hour" as a *factor* level.  I have
>> > found that I can convert the date time to a factor
>> >
>> > time <- as.ordered(cut(time,  "hour"))
>> >
>> > But this produces a factor level for every single day.  The issue I have
>> is
>> > in figuring out how to apply a logical statement to the datetime string
>> or
>> > to the factor.  I would like to say that every datetime with an hour <12
>> is
>> > the morning factor, and every datetime with an hour >12 is at night.
>> Without
>> > LOTS of superfluous code.  below I am going as far as splitting the
>> string
>> > to columns, pulling the time and then setting the factor with a for
>> > statement...yeesh.  I have example CSV dates at the end.
>> >
>> > new.dates <- matrix(unlist(lapply(as.character(dat$Time), function(x)
>> > strsplit(x," "))),ncol=4, byrow=TRUE)  #Break Time String into columns
>> > colnames(new.dates) <- c("day","month","year", "time") # Set column names
>> > dat <- cbind(as.data.frame(new.dates),  as.data.frame(dat)) #bind to data
>> > frame
>> >
>> > tfact<-matrix()
>> >
>> > for (i in which(as.character(dat$time) <= "12:00:00")){
>> >    tfact[i] <- "Morning"
>> >    }
>> >
>> > for (i in which(as.character(dat$time) >= "12:00:00")){
>> >    tfact[i] <- "Night"
>> >    }
>> >
>> > tfact<-factor(tfact,
>> >    levels=c("Morning",  "Night"),
>> >    )
>> >
>> > Example CSV Data
>> > "1","30 Jun 2009 18:14:59"
>> > "2","02 Jul 2009 07:33:37"
>> > "3","06 Jul 2009 08:22:35"
>> > "4","06 Jul 2009 19:25:50"
>> > "5","08 Jul 2009 08:41:48"
>> > "6","10 Jul 2009 07:31:39"
>> > "7","10 Jul 2009 19:59:25"
>> > "8","13 Jul 2009 07:49:18"
>> > "9","13 Jul 2009 18:52:52"
>> > "10","15 Jul 2009 08:06:56"
>> > "11","15 Jul 2009 19:03:01"
>> > "12","17 Jul 2009 08:02:02"
>> >
>> >
>> > Thanks
>> > Pat
>> >
>> > --
>> > Patrick Schmitz
>> > Graduate Student
>> > Plant Biology
>> > 1206 West Gregory Drive
>> > RM 1500
>> >
>> >        [[alternative HTML version deleted]]
>> >
>> > ______________________________________________
>> > R-help at 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.
>> >
>>
>
>
>
> --
> Patrick Schmitz
> Graduate Student
> Plant Biology
> 1206 West Gregory Drive
> RM 1500
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at 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.
>