[R] generating a sequence of seconds

[William Dunlap]

If your activities of interest are mainly during the workday then
seconds-since-3am might give good results, avoiding most daylight
savings time issues.  If they are more biologically oriented then
something like seconds before or after sunrise or sunset might be
better.  Both can be expressed as differences between POSIXct times.
Bill Dunlap
TIBCO Software
wdunlap tibco.com


On Tue, Aug 12, 2014 at 12:26 PM, Erin Hodgess <erinm.hodgess at gmail.com> wrote:
> What I would like to do is to look at several days and determine activities
> that happened at times on those days.  I don't really care which days, I
> just care about what time.
>
> Thank you!
>
>
>
>
> On Tue, Aug 12, 2014 at 3:14 PM, William Dunlap <wdunlap at tibco.com> wrote:
>>
>> > What if I just want the seconds vector without the date, please?  Is
>> > there
>> > a convenient way to create such a vector, please?
>>
>> Why do you want such a thing?  E.g., do you want it to print the time
>> of day without the date?  Or are you trying to avoid numeric problems
>> when you do regressions with the seconds-since-1970 numbers around
>> 1414918800?  Or is there another problem you want solved?
>>
>> Note that the number of seconds in a day depends on the day and the
>> time zone.  In US/Pacific time I get:
>>
>>   > length(seq(from=as.POSIXct("2014-08-12
>> 00:00:00"),to=as.POSIXct("2014-08-12 23:59:59"), by="secs"))
>>   [1] 86400
>>   > length(seq(from=as.POSIXct("2014-03-09
>> 00:00:00"),to=as.POSIXct("2014-03-09 23:59:59"), by="secs"))
>>   [1] 82800
>>   > length(seq(from=as.POSIXct("2014-11-02
>> 00:00:00"),to=as.POSIXct("2014-11-02 23:59:59"), by="secs"))
>>   [1] 90000
>>
>> Bill Dunlap
>> TIBCO Software
>> wdunlap tibco.com
>>
>>
>> On Tue, Aug 12, 2014 at 11:51 AM, Erin Hodgess <erinm.hodgess at gmail.com>
>> wrote:
>> > Hello!
>> >
>> > If I would like to generate a sequence of seconds for a date, I would do
>> > the following:
>> >
>> > x <- seq(from=as.POSIXct(2014-08-12 00:00:00),to=as.POSIXct(2014-08-12
>> > 23:59:59),by="secs")
>> >
>> > What if I just want the seconds vector without the date, please?  Is
>> > there
>> > a convenient way to create such a vector, please?
>> >
>> > thanks,
>> > Erin
>> >
>> >
>> > --
>> > Erin Hodgess
>> > Associate Professor
>> > Department of Mathematical and Statistics
>> > University of Houston - Downtown
>> > mailto: erinm.hodgess at gmail.com
>> >
>> >         [[alternative HTML version deleted]]
>> >
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>
>
>
>
> --
> Erin Hodgess
> Associate Professor
> Department of Mathematical and Statistics
> University of Houston - Downtown
> mailto: erinm.hodgess at gmail.com