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st: Re: Save -tabulate- output as matrix


From   Friedrich Huebler <huebler@rocketmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: Re: Save -tabulate- output as matrix
Date   Fri, 15 Oct 2004 12:06:18 -0700 (PDT)

Stata tech support has confirmed that there is a problem with
-collapse- and the -aweight- option. The problem will be fixed in a
future update.

Friedrich Huebler

--- Friedrich Huebler <huebler@rocketmail.com> wrote:
> Nick,
> 
> Thank you for your program. I deleted the previous messages from
> the
> thread so let me restate what I would like to do: I am looking for
> a way to save -tabulate- output (the frequencies and the percent
> values) as a matrix. The program by Nick works with frequency
> weights
> but when analytic weights are used the matrix is different from the
> -tabulate- output.
> 
> . sysuse auto
> . tab foreign [aw=weight]
> 
>    Car type |      Freq.     Percent        Cum.
> ------------+-----------------------------------
>    Domestic | 57.1261189       77.20       77.20
>     Foreign | 16.8738811       22.80      100.00
> ------------+-----------------------------------
>       Total |         74      100.00
> 
> . friedrich2 foreign [aw=weight], matrix(mat)
> . mat list mat
> 
> mat[2,2]
>                freq    percent
> Domestic         52  70.270271
>  Foreign         22  29.729731
> 
> The original program uses -collapse (count)-. I changed this to
> -collapse (sum)- but the result is the same. The -collapse-
> documentation in the Reference Manual explains that with (count)
> the
> unweighted and analytically weighted results are identical. With
> (sum) I expected the unweighted and analytically weighted results
> to
> be different. My copy of the manual has these definitions on page
> 211:
> 
> sum:
> unweighted: sum(x_j), the sum of the variable
> aweight: sum(v_j*x_j); v_j = (w_j normalized to sum to _N)
> 
> Is my interpretation of the definitions wrong or does -collapse
> (sum)- with analytic weights not do what the manual states?
> 
> Friedrich Huebler
> 
> --- Nick Cox <n.j.cox@durham.ac.uk> wrote:
> > Is this closer to what you want? Not very efficient, so 
> > can be much improved. 
> > 
> > program friedrich2
> > 	version 8
> > 	syntax varname [if] [in] [fweight aweight] , matrix(string) 
> > 
> > 	preserve 
> > 	tempvar freq 
> > 	gen `freq' = 1 
> > 	collapse (count) `freq' `if' `in' [`weight' `exp'],
> by(`varlist') 
> > 	rename `freq' freq 
> > 	egen percent = pc(freq) 
> > 	mkmat freq percent, mat(`matrix') 
> > 
> > 	forval i = 1/`= rowsof(`matrix')' { 
> > 		local name : label (`varlist') `= `varlist'[`i']'
> > 		if `"`name'"' == "" local name = `varlist'[`i']
> > 		if `"`name'"' == "." local name "missing" 
> > 		local names `"`names' `"`name'"' "' 
> > 	} 	
> > 	
> > 	matrix rownames `matrix' = `names' 
> > end 	
> > 	
> > 
> > Nick 
> > n.j.cox@durham.ac.uk


		
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