Re: st: Collecting Statistics of Averages of Variables

[Nick Cox <njcoxstata@gmail.com>]

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Nick

On 28 Sep 2012, at 18:55, robert hartman <rohartman@gmail.com> wrote:

> Hi Listers,
> I'm struggling with a couple of programming challenges. I will start
> with this one. Any input on efficient ways to code this would be most
> appreciated.
>
> I want to take mean (or could be other "egen"/"collapse" type summary
> statistic) form all possible combinations (of subsets of various
> sizes) from a set of variables.
>
> For example, if I have v1, v2, v3, and v4, I would want the mean of
> each: v1v2, v1v3, v1v4, v1v2v3, v1v2v4, v1v3v4...v3v2...v3v2v4, etc.
>
> By v1v2v3, I mean gen v1v2v3=(v1+v2+v3)/3; (assuming the summary
> statistic of interest is the mean)
> by v1v2v3v4, I mean v1v2v3v4=,I mean gen v1v2v3v4=(v1+v2+v3+v4)/4.
>
> etc.
>
> I don't need to actually create permanent variables, simply
> 1. create a temporary "combination variable" (e.g., v1v2v4 =
> rowmean(v1 v2 v4)) for each possible combination,
> 2. collect summary statistics of interest from "combination  
> variables."
> 3. spit out a file that conveys this information intelligibly
>
> For example, I may want to write out a file that gives (a) the name of
> the combination (e.g., v1v2v4--the column representing the rowmean of
> those three variables) and (b) the mean and standard deviation of that
> v1v2v4 variable.
>
> In my particular case, I have about a 70 variable space from which to
> create all these subset combinations.
>
> Any helpful starting points or coding ideas would be helpful.
>
> Thanks,
> Rob Hartman
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