Re: st: date("01jan1960", "DMY") does not seem to work with -if- qualifier of the command -tablist-

["Michael N. Mitchell" <Michael.Norman.Mitchell@gmail.com>]

Dear Jeremy

  This is a most curious issue! Eric provides an excellent solution, but I was still 
flummoxed why the behavior of the -if- condition should be different for my -tablist- 
command as compared to a command like -tabulate-. So, I investigated.

  The heart of -tablist- is the -contract- command. The -if- specification is passed from 
-tablist- to -contract-, and then within the -contract- command it is being implemented 
via the -marksample- command. So I tested the -marksample- command using your if condition.

. clear
. use http://www.stata-press.com/data/r10/datexmpl.dta
. gen statadate = date(bday, "DMY")
. format statadate %td
. local if statadate > date("01Jan1960", "DMY")
. marksample touse, strok novarlist
. list

     +------------------------------------------------+
     | name          bday    x   statadate   __000004 |
     |------------------------------------------------|
  1. | Bill   21 Jan 1952   22   21jan1952          0 |
  2. |  May   11 Jul 1948   18   11jul1948          0 |
  3. |  Sam   12 Nov 1960   25   12nov1960          1 |
  4. |  Kay    9 Aug 1975   16   09aug1975          1 |
     +------------------------------------------------+

The temporary variable __000004 properly indicates that Sam and Kay were born after 
1/1/1960. But, if you look inside the source code of the -contract- command using 
-viewsource contract.ado-, you can see that it is running under version control, using 
-version 6.0-. So, let's try this again, but running the -marksample- command under 
version control.

. version 6.0, missing : marksample touse, strok novarlist
. list

     +-----------------------------------------------------------+
     | name          bday    x   statadate   __000004   __000005 |
     |-----------------------------------------------------------|
  1. | Bill   21 Jan 1952   22   21jan1952          0          0 |
  2. |  May   11 Jul 1948   18   11jul1948          0          0 |
  3. |  Sam   12 Nov 1960   25   12nov1960          1          0 |
  4. |  Kay    9 Aug 1975   16   09aug1975          1          0 |
     +-----------------------------------------------------------+

The new variable created, -__000005-, believes that none of these children were born after 
1/1/1960.

  Unfortunately, we cannot trace this any deeper because the -marksample- command is a 
built in command.

  I think if the -marksample- command (within the -contract- command) were issued using 
version control to bring it to the current version, then I believe that the behavior of 
-contract- with the kind of -if- condition you used would then be consistent across commands.

Best regards,

Michael N. Mitchell
Data Management Using Stata      - http://www.stata.com/bookstore/dmus.html
A Visual Guide to Stata Graphics - http://www.stata.com/bookstore/vgsg.html
Stata tidbit of the week         - http://www.MichaelNormanMitchell.com



On 2011-03-21 5:22 PM, Jeremy Page wrote:
> I am a frequent user of the user generated command -tablist- and I
> have run into a behavior that I can not explain.  I am trying to use
> Stata's -date- command with the -if- qualifier to restrict
> observations from displaying in -tablist-.  When I attempt to do this
> there appears to be a problem.  I am able to use the -date- command to
> restrict observations with -tabulate- and I am able to restrict
> observations in -tablist- with a local variable being defined by the
> -date- command but not with -tablist-.  It is my understanding that
> the -if- qualifiers across all programs should act the same.  Am I
> missing something?  I have included an example below using a Stata
> supplied data set.
>
> I am using version 1.2 of -tablist- which can be found at -findit
> tablist- and my version of Stata is 10.1 on a Windows XP machine.
>
> Thank you for your help.
>
> Best,
> Jeremy
>
>
>
> **********begin example***************
> clear
> use http://www.stata-press.com/data/r10/datexmpl.dta
>
>
> gen statadate = date(bday, "DMY")
>
> format statadate %td
>
> list statadate
>
> display date("01Jan1960", "DMY")
>
> ***it works with tabulate
> tab bday name if statadate>  date("01Jan1960", "DMY")
>
>
> ***it works with a local variable
> local dte = date("01Jan1960", "DMY")
> tablist bday name if statadate>  `dte'
>
> ***it does not work with tablist
> tablist bday name if statadate>  date("01Jan1960", "DMY")
>
>
> ************end example***************
>
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