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Re: st: RE: dates


From   Steven Samuels <sjsamuels@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: RE: dates
Date   Thu, 6 Oct 2011 18:55:42 -0400

Oops! The original algorithm assigned days only from 1 to 15. The correction is below.  A better version  would assign days according to whether the month has 28, 29, 30, or 31 days, but I'll leave that to others.


Steve



With enough missing dates  it might be better to randomly assign a day of the month, or you risk distorting the distribution of inter-visit intervals. 




*********************************
clear
input str10 date
200801
20080113
end
set seed 21932
gen visdate = date(date, "YMD")
tempvar day
gen str2 `day' = string(ceil(30*runiform())) if length(date)==6
replace `day' = "0"+`day' if real(`day')<10
gen fakeday = (length(date)==6)
replace visdate = date(date + `day', "YMD") if length(date)==6
format visdate %td
list date visdate fakeday
*****************************



On Oct 6, 2011, at 5:46 PM, Michael Eisenberg wrote:

Thanks so much.

On Thu, Oct 6, 2011 at 8:23 AM, Nick Cox <n.j.cox@durham.ac.uk> wrote:
> You don't say what "without success" means precisely.
> 
> "200801" does not match either date pattern. If there is no information on day of month, Stata can only return missing for a daily date.
> 
> -date("200801" + "15", "YMD")- seems to be the most common fudge. I would always tag such guessed dates with an indicator variable.
> 
> Nick
> n.j.cox@durham.ac.uk
> 
> Michael Eisenberg
> 
> I have a list of visit dates for patients.  Unfortunately, the format
> is not constant.
> 
> Most are listed with the year, month, day such as 20080105 for Jan 5,
> 2008 but some are listed only with the year and month 200801 for Jan
> 2008.
> 
> I attempted to convert them into stata dates with the commands below
> without success.
> 
> gen ndate = date(dx_date, "YMD")
> or
> gen ndate = date(dx_date, "CCYYNNDD")
> 
> Can stata handle such inconsistent data?
> 
> 
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