R help - Oct 2008 - Time Interval calculation using R

Hi

I have two columns of data with time in form of HH:MM:SS - representing
start time and end time of an activity. I am trying to calculate the time
difference (duration of the activity).

(1) I first tried
> difftime(btime, etime, units = "mins")
This however gave me the error - Error in
as.POSIXlt.character(as.character(x)) :  character string is not in a
standard unambiguous format

(2) The above error message indicated some problem in format. So I
tried
> etime1=as.date(etime, %H:%M:%S")
This gave me the Error: unexpected SPECIAL in "etime1=as.date(etime,
%H:%"

I also tried
>etime1=format(etime, %H:%M:%S")
But this gave a similar error - unexpected SPECIAL in "etime1=format(etime,
%H:%"

Any suggestions?

Regards

	[[alternative HTML version deleted]]

You seem to have omitted a left quotation mark in (2): %H:%M:%S".

Regards,
Yihui
--
Yihui Xie <xieyihui at gmail.com>
Phone: +86-(0)10-82509086 Fax: +86-(0)10-82509086
Mobile: +86-15810805877
Homepage: http://www.yihui.name
School of Statistics, Room 1037, Mingde Main Building,
Renmin University of China, Beijing, 100872, China



On Sun, Oct 5, 2008 at 1:25 PM, Gouri Shankar Mishra
<gouri.mishra at gmail.com> wrote:
> Hi
>
> I have two columns of data with time in form of HH:MM:SS - representing
> start time and end time of an activity. I am trying to calculate the time
> difference (duration of the activity).
>
> (1) I first tried
>> difftime(btime, etime, units = "mins")
> This however gave me the error - Error in
> as.POSIXlt.character(as.character(x)) :  character string is not in a
> standard unambiguous format
>
> (2) The above error message indicated some problem in format. So I tried
>> etime1=as.date(etime, %H:%M:%S")
> This gave me the Error: unexpected SPECIAL in "etime1=as.date(etime,
%H:%"
>
> I also tried
>>etime1=format(etime, %H:%M:%S")
> But this gave a similar error - unexpected SPECIAL in
"etime1=format(etime,
> %H:%"
>
> Any suggestions?
>
> Regards
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>

Seems to work fine for me:
> times <- c("10:12:34", "14:23:15")
> Ptime <- as.POSIXct(strptime(times, "%H:%M:%S"))
>
> Ptime
[1] "2008-10-05 10:12:34 GMT" "2008-10-05 14:23:15 GMT"
> difftime(Ptime[2], Ptime[1], units='min')
Time difference of 250.6833 mins
>
You just have to be careful that all your times are for the same day
since you do not have a 'date' associated with the time.

On Sun, Oct 5, 2008 at 1:25 AM, Gouri Shankar Mishra
<gouri.mishra at gmail.com> wrote:
> Hi
>
> I have two columns of data with time in form of HH:MM:SS - representing
> start time and end time of an activity. I am trying to calculate the time
> difference (duration of the activity).
>
> (1) I first tried
>> difftime(btime, etime, units = "mins")
> This however gave me the error - Error in
> as.POSIXlt.character(as.character(x)) :  character string is not in a
> standard unambiguous format
>
> (2) The above error message indicated some problem in format. So I tried
>> etime1=as.date(etime, %H:%M:%S")
> This gave me the Error: unexpected SPECIAL in "etime1=as.date(etime,
%H:%"
>
> I also tried
>>etime1=format(etime, %H:%M:%S")
> But this gave a similar error - unexpected SPECIAL in
"etime1=format(etime,
> %H:%"
>
> Any suggestions?
>
> Regards
>
>        [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 
Jim Holtman
Cincinnati, OH
+1 513 646 9390

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