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# Re: st: tabstatmat question

 From Nick Cox To statalist@hsphsun2.harvard.edu Subject Re: st: tabstatmat question Date Thu, 1 Sep 2011 21:24:48 +0100

```In addition, -collapse, by(zone wave)- would deliver the means directly.

Nick

On Thu, Sep 1, 2011 at 8:49 PM, Austin Nichols <austinnichols@gmail.com> wrote:
> Sergio <sergioal@ufl.edu>:
> Try (-tabstatmat- is on SSC):
>
> egen byv=group(zone wave), lab
> tabstat num_typ3, stat(mean) by(byv) save
> tabstatmat TABLE
>
> On Thu, Sep 1, 2011 at 3:30 PM, Alvarez,Sergio <sergioal@ufl.edu> wrote:
>> Dear Statalisters,
>>
>> I'm trying to create a matrix of the grouped means of a variable (num_typ3).
>>  The observations in my dataset are grouped by location (zone) and time
>> period (wave).
>>
>> Ideally the matrix would have the zones as the rows and the waves as the
>> columns (or vice-versa), something like this:
>>
>>         WAVE
>> ZONE      1          2       ...
>> 1      mean(1,1)  mean(1,2)
>> 2      mean(2,1)  mean(2,2)
>> ...
>>
>> I would use the matrix to generate a variable that takes the mean value
>> depending on the zone and wave, using something like:
>>
>> gen meancatch = TABLE[zone,wave]
>>
>> I believe I need to go this route, rather than directly creating the
>> variable, because I'm creating a set of 'fake' alternatives for each 'real'
>> observation, corresponding to each location.  Each observation corresponds
>> to a fishing trip, so the alternatives are the possible fishing trips that
>> didn't happen.  I'll do that using -reshape-.
>>
>> Anyway, I thought -tabstatmat- would do the job, so I tried:
>>
>> by zone wave, sort: tabstat num_typ3, stat(mean) save
>>
>> Which gives me the elements of the ideal matrix one by one.  Then I try:
>>
>> tabstatmat TABLE
>>
>> But this returns a 1x1 matrix:
>>
>> symmetric table[1,1]
>>       num_typ3
>> mean  .94892632
>>
>> So my question is, where did I mess up?  Or did I just misunderstand what
>> -tabstatmat- does?  Is there a convenient way to do this?
>>
>>
>> Sergio
>
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