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diff of two timestamps

5 messages · sugo, Gabor Grothendieck, Duncan Mackay +2 more

Original
sugo
# 
Hi all,

I have the following problem: I have a csv-file consisting of timestamp
values (no dates), e.g.:
Timestamp1;Timestamp2;
05:24:43;05:25:05;
15:47:02;15:47:22;
18:36:05;18:36:24;
15:21:24;15:22:04;

I need a vector with the difference of the two timestamps, so I read the
data with the read.csv-function:
myObj <- read.csv("file.csv",header=TRUE,sep=";").

I have then tried unsuccessfully to convert the data to time format (e.g.
using the strptime function like date1 <-
strptime(myObj[0],format="%H:%M:%S")) to be able to perform a datediff
operation.

I would be very grateful if anybody could give me some assistance.

Thanks in advance,
Ieyasu
Gabor Grothendieck
# 
Try this:
+ 05:24:43;05:25:05;
+ 15:47:02;15:47:22;
+ 18:36:05;18:36:24;
+ 15:21:24;15:22:04;"
[1] 00:00:22 00:00:20 00:00:19 00:00:40

See the relevant article in R News 4/1 and its references for more info.
On Wed, Sep 2, 2009 at 7:50 PM, sugo<ieyasu at sugimoto.at> wrote:
Duncan Mackay
# 
Try

require(chron)

dat <- read.table(textConnection("Timestamp1 Timestamp2
05:24:43 05:25:05
15:47:02 15:47:22
18:36:05 18:36:24
15:21:24 15:22:04"), T)
closeAllConnections()

str(dat)
dat[,1] <- times(dat[,1])
dat[,2] <- times(dat[,2])

# numeric
as.numeric(dat[,2] <- times(dat[,2]) )

# test to get seconds from days
86400*as.numeric(dat[,2]-dat[,1])

You may want to check Rnews volume 4(1)

Regards

Duncan Mackay
At 09:50 3/09/2009, you wrote:

            

      
      
      
    

        

      
      
    

  
  


  


      

    

    

      
      

        
      

    

    

      
      

        


  

        

      William Dunlap
    

    

      
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R indices start at 1, not 0, and you should use myObj[,1]
to refer to the first column (myObj[1] means a data.frame
containing one column, myObj[,1] means the first column
itself).  myObj$Timestamp1 and myObj[,"Timestamp1"]
give that column as well.

Hence if you want to use numerical indices try

  > strptime(myObj[,1],format="%H:%M:%S")
  [1] "2009-09-02 05:24:43" "2009-09-02 15:47:02" "2009-09-02 18:36:05"
  [4] "2009-09-02 15:21:24"

but replacing the myObj[,1] with myObj$Timestamp1 will
make things clearer.  with() lets you save some typing by
eliminating the repeated mObj$'s.

  > with(myObj, strptime(Timestamp2,format="%H:%M:%S") -
  +                   strptime(Timestamp1,format="%H:%M:%S"))
  Time differences in secs
  [1] 22 20 19 40
  attr(,"tzone")
  [1] ""

Bill Dunlap
TIBCO Software Inc - Spotfire Division
wdunlap tibco.com