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RE: st: looping


From   "Nick Cox" <n.j.cox@durham.ac.uk>
To   <statalist@hsphsun2.harvard.edu>
Subject   RE: st: looping
Date   Mon, 20 Mar 2006 15:49:22 -0000

Correct.

I guess 

bysort state county age race : egen totalmales = total(males * perwt) 
by state county age race : egen totalfemales = total(females * perwt) 
gen ratio = totalmales / totalfemales 

Nick 
n.j.cox@durham.ac.uk 

Scott Cunningham
 
> On Mar 20, 2006, at 9:42 AM, n j cox wrote:
> 
> > You should read some basic accounts of -by:-.
> >
> > Also, please note the advice in the Statalist FAQ:
> >
> > "Statalist is an international list. Please explain details that  
> > may make sense only in your own corner of the world."
> >
> > Some of the details here presuppose knowledge of your local
> > situation, which I guess to be the United States. It is 
> likely that  
> > many members of Statalist do not know what "msa" means, for example.
> >
> > I am still in the dark on what an observation in your dataset
> > looks like, or what it represents. I assume that -males- and - 
> > females- are numeric variables, but are they dummies or do they  
> > include
> > counts? In either case, what is -perwt- precisely?
> 
> Sorry about the ambiguity.  I did forget my audience.  I am working  
> with a special sample from the 2000 United States Census called the  
> longform.  It is a sample of households - I think 
> approximately 5% of  
> the US population received the survey.  An observation is a  
> household, but since only 5% of all households were sampled, 
> you must  
> use the person weights (-perwt-) when working with this data.  So,  
> for instance, if a certain household is sampled and they represent 5  
> households, then the perwt=5.  Males and females are numeric values.
> 
> >
> > Either way, I guess that -egen, total()- with heavy use of -by()-
> > or -by:- is the easiest way to get totals of males and females,
> > after which you get ratios directly. It should take about 3 lines
> > of Stata. The only looping would be that tacit in -egen-.
> 
> I've been using egen to sum males and females, but was unsure of how  
> to implement the looping over all US county variables.  This 
> is where  
> -by county- wouuld come in, correct?

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