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Re: st: getting Stata to read a bizarre sequence of dates


From   Nick Cox <njcoxstata@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: getting Stata to read a bizarre sequence of dates
Date   Wed, 13 Jun 2012 02:10:54 +0100

You've posted numerous questions on this kind of data over the last
few weeks, to which there have been numerous answers, so why you ask
this question seems especially mysterious.

First, Stata _is_ reading your string dates and it _is_ converting
them to numeric dates. So the implication that Stata can't read these
data is quite wrong.

The only problem evident is that there is one gap in this dataset even
when you restructure it as a series with spacing 28 days.

So, what -tsset- reports is essentially "fair comment". There is a gap
at 638 as the following reveals.

. format edate1 %td

. tab edate1

     edate1 |      Freq.     Percent        Cum.
------------+-----------------------------------
  23nov2008 |          2       14.29       14.29
  28dec2008 |          2       14.29       28.57
  25jan2009 |          2       14.29       42.86
  22feb2009 |          2       14.29       57.14
  29mar2009 |          2       14.29       71.43
  26apr2009 |          2       14.29       85.71
  24may2009 |          2       14.29      100.00
------------+-----------------------------------
      Total |         14      100.00

. tab edate2

     edate2 |      Freq.     Percent        Cum.
------------+-----------------------------------
        637 |          2       14.29       14.29
        639 |          2       14.29       28.57
        640 |          2       14.29       42.86
        641 |          2       14.29       57.14
        642 |          2       14.29       71.43
        643 |          2       14.29       85.71
        644 |          2       14.29      100.00
------------+-----------------------------------
      Total |         14      100.00

By the way, posting code that others can run is an excellent idea, but
cut the -cd d:- which assumes that users have a d: drive, which may be
quite wrong.

Nick

On Wed, Jun 13, 2012 at 12:37 AM, stef salvez <loggyedy@googlemail.com> wrote:

> I have the following panel data set
>
>  clear all
> cd d:\
> input str8  (dates1)            id
>  "23/11/08"         1
> "28/12/08"          1
>  "25/01/09"        1
>  "22/02/09"         1
> "29/03/09"         1
>  "26/04/09"        1
>  "24/05/09"        1
>  "23/11/08"         2
> "28/12/08"          2
>  "25/01/09"        2
>  "22/02/09"        2
> "29/03/09"         2
>  "26/04/09"        2
>  "24/05/09"        2
>
> end
>
> the difference (in days)  between successive dates is 35 28 28 35 28 28
>
> The problem is that I do not know how to convert these string dates
> into numeric variables given the fact that I have 2 jumps  (35 days)
>  if i issue the commands
>
> gen edate1 = date(dates1, "DM20Y")
> gen edate2 = floor(edate1/28)
> tsset id edate2
>
> I get the following error message
>
> panel variable:  id (strongly balanced)
>        time variable:  edate2, 637 to 644, but with gaps
>                delta:  1 unit
>
> Is there any code that could fix that so as to get Stata to "read"
> that "bizarre"sequence of dates?

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