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


From   Nick Cox <njcoxstata@gmail.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 10:58:58 +0100

Sorry, but I am not clear how the second question differs from the first.

One table you are asking for has 300 columns (one for each ID).
Really?  When I have that many columns, I give up on conventional
tables and just go for -list-s. -groups- (SSC) shows my strategy in
action, although I am not promising that it is an answer to any
problem of yours.

On Sat, Sep 22, 2012 at 9:48 AM, Nick Darson <nick.darson@googlemail.com> wrote:
> 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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