[R] return unique values from date/time class object

[Petr Pikal]

Hi Sam

It works for me:

ss<-Sys.time()
sss<-rep(ss,5)
ss<-Sys.time()
sss<-c(sss,ss)
> sss
[1] "2005-08-15 10:04:02 Střední Evropa (letní čas)" "2005-08-15 
10:04:02 Střední Evropa (letní čas)"
[3] "2005-08-15 10:04:02 Střední Evropa (letní čas)" "2005-08-15 
10:04:02 Střední Evropa (letní čas)"
[5] "2005-08-15 10:04:02 Střední Evropa (letní čas)" "2005-08-15 
10:04:35 Střední Evropa (letní čas)"

# six values but only 2 different

> unique(sss)
[1] "2005-08-15 10:04:02 Střední Evropa (letní čas)" "2005-08-15 
10:04:35 Střední Evropa (letní čas)"

# 2 values

> str(sss)
'POSIXct', format: chr [1:6] "2005-08-15 10:04:02" "2005-08-15 
10:04:02" "2005-08-15 10:04:02" "2005-08-15 10:04:02" "2005-
08-15 10:04:02" ...

# posix format as well

HTH
Petr





On 15 Aug 2005 at 16:57, McClatchie, Sam (PIRSA-SARDI) wrote:

> Background:
> OS: Linux Mandrake 10.1
> release: R 2.0.0
> editor: GNU Emacs 21.3.2
> front-end: ESS 5.2.3
> ---------------------------------
> Colleagues
> 
> I have a  wind speed time series with a normal frequency distribution
> and a spike in the 5 metres/second bin. The most likely explanation is
> that the instrument was returning duplicate values at this speed. To
> check  this, I want to extract all the unique times from the series.
> However, unique() works with vectors and the object is POSIXt class.
> I've looked for a similar function to unique() that will work with
> this class, but have failed to find one.
> 
> Any suggestions?
> 
> Thanks
> 
> Sam
> ----
> Sam McClatchie,
> Biological oceanography 
> South Australian Aquatic Sciences Centre
> PO Box 120, Henley Beach 5022
> Adelaide, South Australia
> email <mcclatchie.sam at saugov.sa.gov.au>
> Cellular: 0431 304 497 
> Telephone: (61-8) 8207 5448
> FAX: (61-8) 8207 5481
> Research home page <http://www.members.iinet.net.au/~s.mcclatchie/>
> 
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Petr Pikal
petr.pikal at precheza.cz