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Re: st:-expand- to adjust according to the sampling weight


From   Amanda Fu <mandy.fu1@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st:-expand- to adjust according to the sampling weight
Date   Mon, 20 Dec 2010 23:09:58 -0500

Dear Mr. Samuels,

Thanks for helping me out. It is a smart way to expand the example in
the help file 100 times to see the result. I appreciate it.

Sincerely,
Amanda

On Mon, Dec 20, 2010 at 9:59 PM, Steven Samuels <sjsamuels@gmail.com> wrote:
> Ms. Fu, the FAQ ask that you give the source for unofficial software. Kit
> Baum's -kdens2- does bivariate kernel density plots.  I don't know anything
> about the other commands you referred to.  Try the the example in the -help-
> for -kdens2-, first as written, then as expanded 100 times.  ("expand 100")
> The two graphs will be very different: expansion doesn't work. The command
> you were looking for was "expand weight". As you say, expansion is
> equivalent to the use of frequency weights. The absence of frequency weight
> support in -kdens2-  is not an accident. Apparently there is no way to
> incorporate weights into a -kdens2- analysis.
>
>
> Steven Samuels
>
> sjsamuels@gmail.com
> 18 Cantine's Island
> Saugerties NY 12477
> USA
> Voice: 845-246-0774
> Fax:    206-202-4783
>
>
>
>
> On Dec 20, 2010, at 9:11 PM, Amanda Fu wrote:
>
> Dear Mr. Samuels,
>
> Sorry for not making my question clear. I will keep in mind to provide
> plenty of details in the future.
>
> Here is my response to the questions you listed: The command is
> -kdens2- , -spkde-,-spmap-. They allow neither frequency weights nor
> sampling weights. The data structure is unbalanced panel data.There
> are no clusters and strata. Simply only the sampling weight for each
> individual exists. The purpose of my study is to estimate the
> bivariate kernel density.
>
> I thought I could expand the data based on sampling weights before
> using those commands. I thought I could treat sampling weight similar
> as frequency weight when expanding the data set:
>
> .expand sweight
>
> Even if this command is appropriate, it has a problem: the average
> value for sampling weight in the data set is close to 3000. The
> expanded data set would be too huge. Thus I was thinking to expand
> with a smaller number, say
>
> . sum sweight
> . g new_weight=sweight/r(mean)
> . expand new_weight
>
> This way a number of observations will just remain unchanged after
> expanding. I am not sure if this makes sense.
>
> Thanks for your time!
> Sincerely,
> Amanda
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