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Re: st: Combining date and time into one variable.


From   Svend Juul <SJ@SOCI.AU.DK>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: Combining date and time into one variable.
Date   Fri, 28 Mar 2008 23:55:47 +0100

ippab wrote:
 
I have two variables, one indicating date and another indicating time
of the day.  For example, date = 03/26/2008 and time = 17:31:30.  I am
wondering how I can combine these two variables into one variable so
that I can use the new "Datetime" variable for tis.
 
My understanding is that 'tis' command (for panel data or time series
analysis) only accepts one variable.  Since I have several
observations for a panel on the same day, I need to make sure both
date and time are used as the time variable.
 
=====================================================
 
In Stata 10 the numeric value of a date variable is the number of days 
since 1 January 1960 , and the numeric value of a time variable is the
number of milliseconds since midnight. Before adding them, transform the 
date to milliseconds. 
 
    . clear
    . set obs 1
    . gen date = mdy(3,26,2008)
    . format date %tdNN/DD/CCYY
    . gen time = hms(17,31,30)
    . format time %tcHH:MM:SS
    . list
         +-----------------------+
         |       date       time |
         |-----------------------|
      1. | 03/26/2008   17:31:30 |
         +-----------------------+
 
    . gen double datetime = date*24*60*60*1000 + time
    . format datetime %tcNN/DD/CCYY_HH:MM:SS
    . list
         +---------------------------------------------+
         |       date       time              datetime |
         |---------------------------------------------|
      1. | 03/26/2008   17:31:30   03/26/2008 17:31:30 |
         +---------------------------------------------+

 
Hope this helps
Svend
 
________________________________________________________ 
 
Svend Juul
Institut for Folkesundhed, Afdeling for Epidemiologi
(Institute of Public Health, Department of Epidemiology)
Vennelyst Boulevard 6 
DK-8000 Aarhus C,  Denmark 
Phone, work:   +45 8942 6090 
Phone, home:   +45 8693 7796 
Fax:           +45 8613 1580 
E-mail:        sj@soci.au.dk 
_________________________________________________________ 


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