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st: how to delete observations with missing data


From   sarah smith <sarah22209@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   st: how to delete observations with missing data
Date   Fri, 15 Oct 2004 15:27:13 -0400

Dear STATA users;

I have a panel data and I want to delete the observations where the
data in the variable "name" is missing. I will appreciate if you can
help me.

Thanks,
Sarah


On Thu, 14 Oct 2004 09:27:33 -0700 (PDT), 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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