return unique values from date/time class object

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??edn?? Evropa (letn?? ??as)" "2005-08-15 
10:04:02 St??edn?? Evropa (letn?? ??as)"
[3] "2005-08-15 10:04:02 St??edn?? Evropa (letn?? ??as)" "2005-08-15 
10:04:02 St??edn?? Evropa (letn?? ??as)"
[5] "2005-08-15 10:04:02 St??edn?? Evropa (letn?? ??as)" "2005-08-15 
10:04:35 St??edn?? Evropa (letn?? ??as)"

# six values but only 2 different
unique(sss)
[1] "2005-08-15 10:04:02 St??edn?? Evropa (letn?? ??as)" "2005-08-15 
10:04:35 St??edn?? Evropa (letn?? ??as)"

# 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

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
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return unique values from date/time class object

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