Re: st: converting string to date

[Nilay Kumar <nilaykumar83@gmail.com>]

Hi Nick,

Thanks for your detailed response. I will look at your references in the Stata journal. For now this works. 

thanks again!
Nilay
On Nov 29, 2013, at 1:10 PM, Nick Cox <njcoxstata@gmail.com> wrote:

> I've got to suggest, however, that Stata's own idea of weeks, although
> logical in its own way, rarely if ever corresponds to any other idea
> of weeks. Thus -week()- is likely to make your problems worse.
> 
> This has often been misunderstood, even to the point that it was
> suggested on this list that Stata's implementation of weeks is broken.
> I'll suppress the reference....
> 
> The point is discussed in detail  in my pieces in the Stata Journal,
> but a brief summary here may help.
> 
> Stata's rules are that
> 
> 1. Week 1 of a year always starts on 1 January, regardless.
> 
> 2. Other weeks therefore start 7, 14, 21, ... days later.
> 
> 3. The last week of the year always has 8 or 9 days, depending on
> whether it is not or it is a leap year. So, there are always 52 weeks
> in a year, no more, no less.
> 
> Thus weeks always nest within years.
> 
> If this corresponds to what you want, that's fine. Every other system
> I've seen has the idea either that weeks begin on a certain day of the
> week, or that they end ditto (or clearly, both). The difference lies
> in what is emphasised, not otherwise. It follows that weeks can span
> two years at the end of one year and the beginning of the next.
> 
> 
> 
> Nick
> njcoxstata@gmail.com
> 
> 
> On 29 November 2013 17:51, Nick Cox <njcoxstata@gmail.com> wrote:
>> My mistake: I missed the bit about weeks. Joe Canner has very good
>> advice in his reply.
>> 
>> Weeks in my view are best handled by treating them as daily dates 7 days apart.
>> 
>> See also, if you have a serious interest in weeks,
>> 
>> SJ-12-4 dm0065_1  . . . . . Stata tip 111: More on working with weeks, erratum
>>        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
>>        Q4/12   SJ 12(4):765                                     (no commands)
>>        lists previously omitted key reference
>> 
>> SJ-12-3 dm0065  . . . . . . . . . .  Stata tip 111: More on  working with weeks
>>        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
>>        Q3/12   SJ 12(3):565--569                                (no commands)
>>        discusses how to convert data presented in yearly and weekly
>>        form to daily dates and how to aggregate such data to months
>>        or longer intervals
>> 
>> SJ-10-4 dm0052  . . . . . . . . . . . . . . . . Stata tip 68: Week assumptions
>>        . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .  N. J. Cox
>>        Q4/10   SJ 10(4):682--685                                (no commands)
>>        tip on Stata's solution for weeks and on how to set up
>>        your own alternatives given different definitions of the
>>        week
>> 
>> I'm still proud of the weak "week" pun behind "week assumptions". .
>> 
>> 
>> 
>> Nick
>> njcoxstata@gmail.com
>> 
>> 
>> On 29 November 2013 17:47, Nick Cox <njcoxstata@gmail.com> wrote:
>>> This works fine:
>>> 
>>> . di %td date("2004-01-04", "YMD")
>>> 04jan2004
>>> 
>>> Note the very simple -- but  from many posts on this list seemingly
>>> little known -- technique of trying out a simple example using the
>>> -display- command and a format that checks whether I get the right
>>> answer.
>>> 
>>> But your approach also works fine in the examples I tried
>>> 
>>> . di %td date("2004-01-04", "20YMD")
>>> 04jan2004
>>> . di %td date("1998-01-04", "20YMD")
>>> 04jan1998
>>> 
>>> so why did you say "does not seem to work"? Did you forget to assign a
>>> date format so that what you see is human-readable?
>>> 
>>> 
>>> Nick
>>> njcoxstata@gmail.com
>>> 
>>> 
>>> On 29 November 2013 17:15, Nilay Kumar <nilaykumar83@gmail.com> wrote:
>>>> I have a dataset where weeks are listed as strings ie. 2004-01-04 - 2004-01-10. How can I convert this entire string to dates?
>>>> I tried gen date1= date(var, “20YMD”) but that does not seem to work for this
> 
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