[R] Question on creating Date variable

[David Winsemius]

On Dec 31, 2012, at 11:35 AM, Christofer Bogaso wrote:

> On 01 January 2013 00:17:50, David Winsemius wrote:
>>
>> On Dec 31, 2012, at 9:12 AM, Christofer Bogaso wrote:
>>
>>> Hello all,
>>>
>>> Let say I have following (numeric) vector:
>>>
>>> > x
>>> [1] 11.00 11.25 11.35 12.01 11.14 13.00 13.25 13.35 14.01 13.14  
>>> 14.50
>>> 14.75 14.85 15.51 14.64
>>>
>>> Now, I want to create a 'Date' variable (i.e. I should be able to do
>>> all calculations pertaining to date/time and also time-series
>>> plotting etc.) like
>>>
>>> 2012-12-31 11:00:00 AM, 2012-12-31 11:25:00 AM, 2012-12-31 11:35:00
>>> AM, 2012-12-31 12:01:00 PM, . . . .
>>>
>>
>> Those _times_ ( _not_ Dates) cannot possibly be in %M.%S" format,
>> given the number of items to the right of the decimal point that are
>> greater than 60. So will proceed on the arguably more likely
>> assumption that they are in fractional minutes. To recover from that
>> problem, one might consider:
>>
>> > as.POSIXct(paste( floor(x), round(60*(x-floor(x))) ), format="%M  
>> %S")
>> [1] "2012-12-31 00:11:00 PST" "2012-12-31 00:11:15 PST"
>> [3] "2012-12-31 00:11:21 PST" "2012-12-31 00:12:01 PST"
>> [5] "2012-12-31 00:11:08 PST" "2012-12-31 00:13:00 PST"
>> [7] "2012-12-31 00:13:15 PST" "2012-12-31 00:13:21 PST"
>> [9] "2012-12-31 00:14:01 PST" "2012-12-31 00:13:08 PST"
>> [11] "2012-12-31 00:14:30 PST" "2012-12-31 00:14:45 PST"
>> [13] "2012-12-31 00:14:51 PST" "2012-12-31 00:15:31 PST"
>> [15] "2012-12-31 00:14:38 PST"
>>
>
> I understand that some of those elements are not "dates". However  
> what I want is the ***"PM/AM" suffix*** on those elements which are  
> considered as Dates.
>
> ***Getting those suffix*** and doing calculations on those changed  
> variables is my primary concern.

That's the first time that AM/PM has bee mentioned and I suppose if  
those were fractional hours rather than my guess of fractional minutes  
that there might be representatives of both in the numeric data you  
offered. Why don't you clarify what these number do in fact represent?  
And what problem you are trying to solve?

-- 


David Winsemius, MD
Alameda, CA, USA