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st: RE: Identify min and max observations


From   "Martin Weiss" <martin.weiss1@gmx.de>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: RE: Identify min and max observations
Date   Sun, 27 Sep 2009 15:41:55 +0200

<>

You want your admdate to be numeric for sure. You could then -sort- within
id and take the first and last value. A more general solution is:

**************
clear*

inp id str10  admdate      
1  12may06       
1  20jun06
1  30aug06       
2  10may06       
2  10sep06
2  20dec06
2  10jan07       
3  10aug06       
3  20sep06
3  10dec06
3  15jan07
3  10feb07  
end

compress

gen date=date(admdate, "DM20Y")
format date %tdMonth_DD,_CCYY

list, noobs  

tempvar min max
bys id: egen `min'=min(date)
bys id: egen `max'=max(date)

bys id: gen byte mindate=date==`min'
bys id: gen byte maxdate=date==`max'

list, noobs sepby(id)
**************


HTH
Martin


-----Original Message-----
From: owner-statalist@hsphsun2.harvard.edu
[mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Thomas Cars
Sent: Sonntag, 27. September 2009 14:18
To: statalist@hsphsun2.harvard.edu
Subject: st: Identify min and max observations

Hi,
I have a dataset including subjects (id) and date for administration  
of a specific drug (adm.date)

I now want to construct a variable telling me which one of the  
observations (adm.date) in each subject (id) that has the lowest date  
(min) and the highest date(max).

The number of adm.date can vary in each subject from 1 to 10.


Example (min=1 och max=2)



Id                   adm.date        min/max

1                    12may06         1
1                    20jun06
1                    30aug06         2
2                    10may06         1
2                    10sep06
2                    20dec06
2                    10jan07         2
3                    10aug06         1
3                    20sep06
3                    10dec06
3                    15jan07
3                    10feb07         2

And so on?

I hope anyone can help me!

Thomas


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