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Re: st: wrong datetime results with clock() -- sometimes


From   Nick Cox <njcoxstata@gmail.com>
To   "statalist@hsphsun2.harvard.edu" <statalist@hsphsun2.harvard.edu>
Subject   Re: st: wrong datetime results with clock() -- sometimes
Date   Fri, 5 Jul 2013 20:50:13 +0100

There is a very interesting meta-issue. I guess wildly that people at
StataCorp may well have discussed this.

It was not so very long ago that if you did something like

gen foo = "Stata strings sweetly sing"

that would be an error unless you spelled out something like

gen str26 foo = ...

but now Stata is smart enough to work out that the variable being
generated must be string. So, why does not Stata see e.g. -clock()- on
the right-hand side and automatically produce a -double-?

My guess is two-fold.

1. Stata still follows an "you're an adult and take responsibility for
what you say" attitude to -generate- and variable types.

2. The presence of -clock()- on the right-hand side does not itself
guarantee that a -double- is needed, as in principle -clock()- might
be part of a larger calculation for which -double-s are _not_
required.

Nick
njcoxstata@gmail.com


On 5 July 2013 20:36, Rebecca Pope <rebecca.a.pope@gmail.com> wrote:
> Austin,
> Thanks. That was precisely the problem. I made an assumption about the
> variable being automatically generated in double format. It turns out
> that StataCorp has not yet implemented mind-reading.
>
> Feeling very foolish now,
> Rebecca
>
> On Fri, Jul 5, 2013 at 2:28 PM, Austin Nichols <austinnichols@gmail.com> wrote:
>> Rebecca Pope <rebecca.a.pope@gmail.com>:
>> Try a double.
>>
>> clear all
>> input str21 timestr
>> " 2/8/2011 9:50:51 PM"
>> "2/12/2011 4:15:40 PM"
>> "2/11/2011 3:26:12 PM"
>> "5/15/2011 9:46:41 AM"
>> "5/20/2011 8:32:28 PM"
>> " 2/7/2011 2:15:40 PM"
>> "5/25/2011 7:07:57 PM"
>> " 5/9/2011 3:00:42 PM"
>> "5/22/2011 3:24:57 PM"
>> " 5/9/2011 7:09:46 PM"
>> end
>> gen dt=clock(timestr,"MDYhms")
>> gen double dt2=clock(timestr,"MDYhms")
>> format dt dt2 %tc
>> li
>>
>> On Fri, Jul 5, 2013 at 3:05 PM, Rebecca Pope <rebecca.a.pope@gmail.com> wrote:
>>> Hello,
>>> I am trying to convert a variable with datetime observations currently
>>> stored as string to a numeric format. Here is a sample of my data
>>> after issuing these command:
>>>
>>> gen datetime = clock(timestr,"MDYhms")
>>> format datetime %tc
>>>
>>> . list timestr datetime in 1/10, noobs clean
>>>                  timestr             datetime
>>>      2/8/2011 9:50:51 PM   08feb2011 21:50:37
>>>     2/12/2011 4:15:40 PM   12feb2011 16:14:48
>>>     2/11/2011 3:26:12 PM   11feb2011 15:27:08
>>>     5/15/2011 9:46:41 AM   15may2011 09:46:59
>>>     5/20/2011 8:32:28 PM   20may2011 20:31:39
>>>      2/7/2011 2:15:40 PM   07feb2011 14:16:37
>>>     5/25/2011 7:07:57 PM   25may2011 19:08:51
>>>      5/9/2011 3:00:42 PM   09may2011 15:01:44
>>>     5/22/2011 3:24:57 PM   22may2011 15:25:01
>>>      5/9/2011 7:09:46 PM   09may2011 19:10:46
>>>
>>> As you can see, the converted values are a few seconds off from the
>>> time stored in the string variable.
>>>
>>> I don't think that this is a Stata problem per se because if I convert
>>> a single observation, the correct time is displayed:
>>> . di %tc clock("2/8/2011 9:50:51 PM", "MDYhms")
>>> 08feb2011 21:50:51
>>>
>>> That said, I'm not the first person to encounter this
>>> (http://www.stata.com/statalist/archive/2011-10/msg00687.html).
>>> However, I don't see that a solution/reason was ever provided.
>>>
>>> My best guess in the face of this was a hidden character in the
>>> variable. I checked for this with the following:
>>> replace timestr = subinstr(" "+timestr+" "," ","-",.) in 1/10
>>>                    timestr
>>>      -2/8/2011-9:50:51-PM-
>>>     -2/12/2011-4:15:40-PM-
>>>     -2/11/2011-3:26:12-PM-
>>>     -5/15/2011-9:46:41-AM-
>>>     -5/20/2011-8:32:28-PM-
>>>      -2/7/2011-2:15:40-PM-
>>>     -5/25/2011-7:07:57-PM-
>>>      -5/9/2011-3:00:42-PM-
>>>     -5/22/2011-3:24:57-PM-
>>>      -5/9/2011-7:09:46-PM-
>>>
>>> As you can see, the hyphens are right next to the text, so I don't
>>> think there is anything lurking at the beginning or end of the text
>>> that isn't displaying.
>>>
>>> Does anyone have other suggestions?
>>>
>>> Thanks,
>>> Rebecca
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