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Re: st: dates in stata


From   "E. Paul Wileyto" <epw@mail.med.upenn.edu>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: dates in stata
Date   Tue, 31 Mar 2009 17:14:07 -0400

Your date is entered as a string, not a real date format. Real dates are integer values, representing (currently) the number of days elapsed since January 1st 1960.
Try this:
. edit
(1 var, 13 obs pasted into editor)

. list

     +------------------+
     |             var1 |
     |------------------|
  1. |    01 April 2005 |
  2. |    01 April 2008 |
  3. |   01 August 2000 |
  4. |   01 August 2001 |
  5. |   01 August 2002 |
     |------------------|
  6. |   01 August 2003 |
  7. |   01 August 2005 |
  8. |   01 August 2006 |
  9. |   01 August 2007 |
 10. |   01 August 2008 |
     |------------------|
 11. | 01 December 2000 |
 12. | 01 December 2003 |
 13. | 01 December 2004 |
     +------------------+

. gen dateval=date( var1, "DMY")

. list

     +----------------------------+
     |             var1   dateval |
     |----------------------------|
  1. |    01 April 2005     16527 |
  2. |    01 April 2008     17623 |
  3. |   01 August 2000     14823 |
  4. |   01 August 2001     15188 |
  5. |   01 August 2002     15553 |
     |----------------------------|
  6. |   01 August 2003     15918 |
  7. |   01 August 2005     16649 |
  8. |   01 August 2006     17014 |
  9. |   01 August 2007     17379 |
 10. |   01 August 2008     17745 |
     |----------------------------|
 11. | 01 December 2000     14945 |
 12. | 01 December 2003     16040 |
 13. | 01 December 2004     16406 |
     +----------------------------+

. format  dateval %d

. list

     +------------------------------+
     |             var1     dateval |
     |------------------------------|
  1. |    01 April 2005   01apr2005 |
  2. |    01 April 2008   01apr2008 |
  3. |   01 August 2000   01aug2000 |
  4. |   01 August 2001   01aug2001 |
  5. |   01 August 2002   01aug2002 |
     |------------------------------|
  6. |   01 August 2003   01aug2003 |
  7. |   01 August 2005   01aug2005 |
  8. |   01 August 2006   01aug2006 |
  9. |   01 August 2007   01aug2007 |
 10. |   01 August 2008   01aug2008 |
     |------------------------------|
 11. | 01 December 2000   01dec2000 |
 12. | 01 December 2003   01dec2003 |
 13. | 01 December 2004   01dec2004 |
     +------------------------------+

. sort dateval

. list

     +------------------------------+
     |             var1     dateval |
     |------------------------------|
  1. |   01 August 2000   01aug2000 |
  2. | 01 December 2000   01dec2000 |
  3. |   01 August 2001   01aug2001 |
  4. |   01 August 2002   01aug2002 |
  5. |   01 August 2003   01aug2003 |
     |------------------------------|
  6. | 01 December 2003   01dec2003 |
  7. | 01 December 2004   01dec2004 |
  8. |    01 April 2005   01apr2005 |
  9. |   01 August 2005   01aug2005 |
 10. |   01 August 2006   01aug2006 |
     |------------------------------|
 11. |   01 August 2007   01aug2007 |
 12. |    01 April 2008   01apr2008 |
 13. |   01 August 2008   01aug2008 |
     +------------------------------+

.







lschoele@rumms.uni-mannheim.de wrote:
Hello Statalist,

I am using Stata for event study. I entered all my variables and observations. Regarding my variable "date" I have a problem. When I use "sort date", stata sorts the date shown above:date
01 April 2002
01 April 2003
01 April 2004
01 April 2005
01 April 2008
01 August 2000
01 August 2001
01 August 2002
01 August 2003
01 August 2005
01 August 2006
01 August 2007
01 August 2008
01 December 2000
01 December 2003
01 December 2004
01 December 2005
01 December 2006
01 February 2000
01 February 2001
01 February 2002
01 February 2005
01 February 2006
01 February 2007
01 February 2008
01 July 2002
01 July 2003
01 July 2004
01 July 2005
01 July 2008
01 June 2000
01 June 2001
01 June 2004
01 June 2005
01 June 2006
01 June 2007
01 March 2000
01 March 2001
01 March 2002
01 March 2004
01 March 2005
01 March 2006
01 March 2007
01 May 2000
01 May 2001

I can tell that stata sorts by the first letter of the month. Do I have to use a special format for the date? I also tried the format 01.04.2002, but that gives me the same sortation shown above.

Can anyone help me?

Best regards
Lisa



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--
E. Paul Wileyto, Ph.D.
Assistant Professor of Biostatistics
Tobacco Use Research Center
School of Medicine, U. of Pennsylvania
3535 Market Street, Suite 4100
Philadelphia, PA  19104-3309

215-746-7147
Fax: 215-746-7140
epw@mail.med.upenn.edu



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