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st: tabstatmat question


From   "Alvarez,Sergio" <sergioal@ufl.edu>
To   <statalist@hsphsun2.harvard.edu>
Subject   st: tabstatmat question
Date   Thu, 01 Sep 2011 15:30:37 -0400

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?

Thanks in advance,

Sergio


--
Sergio Alvarez
Food and Resource Economics
University of Florida

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