Hi Ogbos,
Remember that there is an underlying numeric representation of dates.
as.Date assigns dates a number of days from an agreed origin
(1970-01-01) while POSIX dates assign a number of seconds. If you plot
in one system and then try to add points in another, it's not going to
work.
Jim
On Sun, Feb 17, 2019 at 12:55 PM Ogbos Okike <giftedlife2...@gmail.com> wrote:
>
> Dear Jim,
> Thank you and welcome back. It seems you have been away as you have not been
> responding to people's questions as before.
>
> I have just made a correction on my original question. Please have a look and
> check if I can still go the way u have suggested or if the correction would
> call for another approach.
> Best regards
> Ogbos
>
>
> On Sun, Feb 17, 2019, 02:22 Jim Lemon <drjimle...@gmail.com> wrote:
>>
>> Hi Ogbos,
>> It may be easier to use strptime:
>>
>> dta<-data.frame(year=rep(2005,5),month=rep("05",5),
>> day=c("01","06","11","16","21"),
>> hour=c(2,4,6,8,10),minute=rep(0,5),second=rep(0,5),value=1:5)
>> dta$Ptime<-strptime(paste(paste(dta$year,dta$month,dta$day,sep="-"),
>> paste(dta$hour,dta$minute,dta$second,sep=":")),"%Y-%m-%d %H:%M:%S")
>> plot(dta$Ptime,dta$value)
>> text(strptime("2005-05-04 09:00:00","%Y-%m-%d %H:%M:%S"),4,"b")
>>
>> Jim
>>
>> > On February 16, 2019 1:08:38 PM PST, Ogbos Okike
>> > <giftedlife2...@gmail.com> wrote:
>> > >Dear Jeff,
>> > >One more problem please.
>> > >
>> > >When I used as.Date(ISOdate(dta$year, dta$month, dta$day,dta$hour)) to
>> > >handle date, I could use text(as.Date("2005-03-13"),-9,"b") to label
>> > >my plot.
>> > >
>> > >Now that I am using as.POSIXct(ISOdatetime(year,
>> > >month,day,hour,0,0))), can you please tell me how to text "b" on the
>> > >point corresponding with 1960-05-04 09:00:00 on my plot.
>> > >
>> > >Many thanks for your extra time.
>> > >
>> > >Best wishes
>> > >Ogbos
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