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return unique values from date/time class object

3 messages · McClatchie, Sam (PIRSA-SARDI), PIKAL Petr, Brian Ripley

Original
McClatchie, Sam (PIRSA-SARDI)
# 
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/>
  
                   /\
      ...>><xX(??> 
                //// \\\\
                   <??)Xx><<
              /////  \\\\\\
                        ><(((??> 
  >><(((??>   ...>><xX(??>O<??)Xx><<
PIKAL Petr
# 
Hi Sam

It works for me:

ss<-Sys.time()
sss<-rep(ss,5)
ss<-Sys.time()
sss<-c(sss,ss)
[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
[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
'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:

            

      
      
      
    

        

      
      
    

        
Petr Pikal
petr.pikal at precheza.cz

  
  


  


      

    

    

      
      

        


  

        

      Brian Ripley
    

    

      
      #
    

  


  

      
On Mon, 15 Aug 2005, McClatchie, Sam (PIRSA-SARDI) wrote:

        

            

      
      
      
    

        
Time for an update.

            

      
      
      
    

        
foo[!duplicated(unclass(foo))]

works, for POSIXct (POSIXt is a virtual class covering that and POSIXlt: 
for the latter convert to POSIXct).