<>
Nick`s http://www.stata-journal.com/sjpdf.html?articlenum=pr0007 may help
you get a handle on such issues. The -if- qualifier is not really a good
idea with -egen- functions, but some of them do allow you to specify
-expression-s which evaluate to 1 or 0, and can thus be useful when
multiplied with something else, or even on their on, as in my example.
HTH
Martin
-----Original Message-----
From: [email protected]
[mailto:[email protected]] On Behalf Of Johannes Schoder
Sent: Mittwoch, 16. September 2009 00:39
To: [email protected]
Subject: Re: AW: st: Different Results for the same estimation
I found another bug in my calculations:
Since I have the number of diagnosed cancer cases per cancer type,
county, and the survival time in months I wanted to calculate the
number of people surviving one year per county and cancer type. However
I did it wrong.
How can I generate a variable that gives my the number of people who
survived 12 months?
bysort CancerType COUNTY: egen N_SurvivorsOneYear =
count(time_in_months) if time_in_months>12
When time_in_months<12 N_SurvivorsOneYear gets zero or "." (missing value)
but I want that it takes the value of the number of survivors per
disease and per county.
I know my description sounds confusing here is an example:
id time_in_months county N_survivorsOneYear cancer type
1 13 01
2 breast
2 14 02
2 breast
3 1 03
. breast
instead of the "." missing value for id 3 and N_survivorsOneYear I want
to have "2"
Thanks a lot for your help!
Johannes
Martin Weiss schrieb:
> <>
>
>
> You can always -collapse- or make up a fake identifier as
>
>
> -bys County disease: gen personid=_n-
> -la var personid "Fake Identifier"-
>
>
> To appreciate the meaning of this command, check Nick`s
> http://www.stata-journal.com/sjpdf.html?articlenum=pr0004
>
>
>
> HTH
> Martin
>
>
> -----Ursprüngliche Nachricht-----
> Von: [email protected]
> [mailto:[email protected]] Im Auftrag von Johannes
> Schoder
> Gesendet: Dienstag, 15. September 2009 22:16
> An: [email protected]
> Betreff: Re: st: Different Results for the same estimation
>
> Hi Martin:
> Thanks a lot for your help.
> Yes you are right I have nesting levels, within counties there are
> diseases that afflict individuals.
> Unfortunately I messed (or the data provider) something up when
> importing the data. I just realized that I have a lot of individuals
> with the same identifier variable (although they are not the same), so I
> can't really use the id number.
> Is there any alternative of aggregating the individual level data to the
> county level?
> Johannes
>
>
> Martin Weiss schrieb:
>
>> <>
>>
>>
>> So there are three nesting levels? Within counties, there are diseases
>> afflicting individuals? If that is the case, you should amend your
command
>> as
>>
>> - bysort County disease (individual): keep if _n==1-
>>
>> to make it stable for the -glm- analysis. "individual" should be replaced
>>
> by
>
>> some identifier variable, like an id number.
>>
>>
>> Also look at -egen, tag()- as -drop-ping is not generally the best
>>
> approach
>
>> to conducting a restricted analysis ("How are you going to get the
dropped
>> obs back when you need them quickly?").
>>
>> Also look at -xtmixed- and its brothers, as your analysis sounds like a
>>
> good
>
>> case for them...
>>
>>
>> HTH
>> Martin
>>
>> -----Original Message-----
>> From: [email protected]
>> [mailto:[email protected]] On Behalf Of Johannes
>>
> Schoder
>
>> Sent: Dienstag, 15. September 2009 20:17
>> To: [email protected]
>> Subject: Re: st: Different Results for the same estimation
>>
>> I found the bug:
>>
>> Since I am using the following command before the estimation:
>> bysort County disease: keep if _n==1
>> Stata probably kicks out different obervations eacht time.
>> Does someone knows how to avoid that? A similar question was posed a
>> couple of days ago:
>> How to delete duplicate observations, Martin recommended the following
>> command that I used (see above):
>>
>> bysort ID: keep if_n==1
>>
>>
>>
>> However my problem is not exactly the same:
>> Since I would like to aggregate my individual level data to the county
>> level I would like to just keep one observation for each county [instead
>> of keeping one observation per county I would like to keep 98
>> observations per county (one observation per county and per cancer type;
>> there are 98 different cancer types)].
>> Therefore the observations I would like to drop are not the same
>> individuals, they just live in the same county and suffer from the same
>> disease.
>>
>> Thanks for your help!!
>> Johannes
>>
>>
>>
>>
>>
>>
>> Johannes Schoder schrieb:
>>
>>
>>> Dear Statalist users:
>>>
>>> When I am estimating the same model several times afterwards (with the
>>> same computer):
>>> xi: glm [dep. var.] [indep. var.] i.county i.year, family (binomial
>>> weight) link(logit)
>>>
>>> I get different results for the exactly same specification.
>>> Does anyone know whats going on here? Is it because of the different
>>> number of iterations (sometimes 8,9 or 10)?
>>> Which results are right? What can I do to get the identical result for
>>> the same estimation?
>>> Thanks a lot for any suggestion!
>>> Johannes
>>>
>>> *
>>> * For searches and help try:
>>> * http://www.stata.com/help.cgi?search
>>> * http://www.stata.com/support/statalist/faq
>>> * http://www.ats.ucla.edu/stat/stata/
>>>
>>>
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/statalist/faq
>> * http://www.ats.ucla.edu/stat/stata/
>>
>>
>> *
>> * For searches and help try:
>> * http://www.stata.com/help.cgi?search
>> * http://www.stata.com/support/statalist/faq
>> * http://www.ats.ucla.edu/stat/stata/
>>
>>
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
>
> *
> * For searches and help try:
> * http://www.stata.com/help.cgi?search
> * http://www.stata.com/support/statalist/faq
> * http://www.ats.ucla.edu/stat/stata/
>
*
* For searches and help try:
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* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
*
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* http://www.stata.com/support/statalist/faq
* http://www.ats.ucla.edu/stat/stata/
