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Re: st: generating age using dates


From   Neil Shephard <nshephard@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: generating age using dates
Date   Fri, 17 Dec 2010 17:05:11 +0000

On Fri, Dec 17, 2010 at 4:56 PM, martine etienne <martieluvsu@yahoo.com> wrote:
> Thanks Neil,
> "very similiar" looks like this:
>
> tab age
>
>        age |      Freq.     Percent        Cum.
> ------------+-----------------------------------
>   49.85495 |          1        0.35        0.35
>   49.86043 |          1        0.35        0.70
>   49.86864 |          1        0.35        1.05
>   49.87685 |          1        0.35        1.39
>   49.89053 |          2        0.70        2.09
>   49.90421 |          1        0.35        2.44
>   49.90695 |          1        0.35        2.79
>   49.91516 |          2        0.70        3.48
>   49.92337 |          2        0.70        4.18
>   49.92611 |          1        0.35        4.53
>   49.93705 |          2        0.70        5.23
>   49.93979 |          1        0.35        5.57
>   49.94253 |          1        0.35        5.92
>   49.94527 |          3        1.05        6.97
>     49.948 |          1        0.35        7.32
>   49.95348 |          1        0.35        7.67
>

That clarifies that there are people of similar age that is your
problem, from your original posting it wasn't clear (to me) whether
this was your problem or the variables 'age' and 'nage'  were very
similar (which would have been unlikely based on the code posted).

> please see the output of
>
> des nage age
>
>              storage  display     value
> variable name   type   format      label      variable label
> ----------------------------------------------------------------------------------------------------------------------
>
> nage            float  %9.0g
> age             float  %9.0g
>
> The survey was administered to a random selection of patients, and our patient
> population is between 20-60years old.
>
>
> any thoughts?

How is the data formatted before you converted to %td variables?
Could it be that some years are two-digits whilst others are four?

How much missing data is there in the original "Date of Birth" and
"Survey date" variables and how are missing dates handled?

Neil

-- 
"Our civilization would be pitifully immature without the intellectual
revolution led by Darwin" - Motoo Kimura, The Neutral Theory of
Molecular Evolution

Email - nshephard@gmail.com
Website - http://kimura-no-ip.org/
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