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Re: st: creating cross tables/ matrices with expected/ observed frequencies from long data set


From   Nick Darson <nick.darson@googlemail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: creating cross tables/ matrices with expected/ observed frequencies from long data set
Date   Sat, 22 Sep 2012 18:48:24 +1000

Well, if there is not other solution, I guess I will have to reshape
the data. I just wanted to double check whether there is a "tab"-like
command that can create cross-tabs of different groups from the same
variable....

What about the second question (for the expected frequencies)? Is
there any table function (in the sense of "list") that simply shows
the values of a group from a variable instead of describing its
summary/ modes/ etc?

BTW: Thanks for the reply, Nick!



On Sat, Sep 22, 2012 at 5:16 PM, Nick Cox <njcoxstata@gmail.com> wrote:
> I think that this question is self-cancelling, as I guess that you
> need to restructure your data to get tables that you want, but seem to
> rule that out as an acceptable solution.
>
> Nick
>
> On Sat, Sep 22, 2012 at 1:35 AM, Nick Darson <nick.darson@googlemail.com> wrote:
>
>> I would like to create several tables/matrices with expected
>> frequencies and observations (to be able to carry out a Chi Square
>> test of how well my model describes the data).
>> I have the following data set (each person chose from 2 sets, the
>> first one containing 3 option, the second one containing 4 options),
>> with ID=individuals (300), set=choice set, option= option, choice=
>> chosen option (dummy), Prob= expected probability for each individual
>> based on my random-effects logit model.
>>
>> ID      Set     Option    Choice                Prob
>> 1       1       A               0               0.2
>> 1       1       B               1               0.7
>> 1       1       C               0               0.1
>> 1       2       D               0               0.1
>> 1       2       E               0               0.2
>> 1       2       F               1               0.4
>> 1       2       G               0               0.3
>> 2….
>>
>> First I would need a cross-table with observed frequencies for the two
>> choice sets (looking as follows):
>>       A  B  C
>> D
>> E
>> F
>> G
>>
>> I am familiar with the tab-command, but a bit lost how do to obtain
>> the table given my data-set arrangement? Any help would be
>> appreciated.
>>
>>
>> Then I would need the same table as above, but with expected (joint)
>> probabilities instead of observed frequency. For this, I had the
>> following strategy in mind:
>> 1.) Create 2 matrices, one for each choice set
>> 2.) Transpose one matrix and multiply to obtain joint probability
>>
>> For 1.), I would need one table with the probabilities listed (column=
>> Individuals; rows= options) as follows:
>>
>>         ID1    ID2       ID3 …..
>> A     0.2          …..
>> B     0.7
>> C    0.1
>> (and same table/ matrix for set 2).
>> How would I do this in Stata? To my understanding, Tabs and tabstats
>> only provide summaries etc, but I want the original value of prob
>> listed?
>> Any help would be appreciated!
>> BTW: this is a simplification of the original data set (more sets and
>> options) and I would like to do several things in one set…therefore, I
>> “keep”/”reshape” combos would not be suitable.
>>
>
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