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RE: st: Counting firms in a panel dataset


From   "Miguel A. Duran" <[email protected]>
To   <[email protected]>
Subject   RE: st: Counting firms in a panel dataset
Date   Thu, 16 Jan 2014 13:29:17 +0100

Thanks, Nick. This simple (and elegant) solution works. And my intuition
about the differences between the numbers of agents counted was right.

Best,
Miguel.

-----Mensaje original-----
De: [email protected]
[mailto:[email protected]] En nombre de Nick Cox
Enviado el: jueves, 16 de enero de 2014 13:17
Para: [email protected]
Asunto: Re: st: Counting firms in a panel dataset

This helps; thanks. You can identify individuals without data for their
start dates by

egen start_info = total(date == startdate), by(id)

and then look at observations

... if start_info == 0

Nick
[email protected]


On 16 January 2014 12:10, Miguel A. Duran <[email protected]> wrote:
> Nick, thanks for your help. I will try to be clearer. There is no 
> fallacy in your logic argument, but this is not the problem. In 
> addition, what I am showing is a simplified version of the relevant 
> part of my dataset (the whole dataset has 178,410 observations and 
> about 40 variables), just to illustrate what I mean.
> These are the codes I am using:
> In this simplified version:
> -codebook id if mean_var1 != 11- counts both agents (408 in my dataset).
> -codebook id if mean_var1 != 11 & (var1 == 10/var2 | var1 == 11/var2)- 
> counts 1 agent (id1) (397 in my dataset).
> But -codebook id if mean_var1 != 11 & !(var1 == 10/var2 | var1 == 
> 11/var2)- also counts both agents. The reason is because -(var1 == 
> 10/var2 | var1 ==
> 11/var2)- focuses on any value of var1 equal to 10 or 11 if var2 == 1 
> (ie, if startdate == date).  Nevertheless, -!(var1 == 10/var2 | var1 
> == 11/var2)- refers to any observation where var1 and var2 are not 
> equal to 10 or 11 regardless the value of var2. Therefore, 
> observations 1, 2 and 4 for id1 and
> 5-8 for id2 are taken into account, ie, both agents are counted.
> What I want to count is agents (i) whose mean_var is not equal to 11, 
> (ii) and have no observation in the date of the startdate (eg, for 
> id2, startdate = 192, but there is no observation for that date). 
> Please, note that the latter requirement is not having a missing value 
> when startdate == date, but that there is no observation.
>
> obs  id     startdate    date   var1      var2    mean_var1
>  1      1           189          187     10           .         10.75
>  2      1           189          188     11           .         10.75
>  3      1           189          189     11           1        10.75
>  4      1           189          190     11           .         10.75
>  5      2           192          189     10           .         10.5
>  6      2           192          190     10           .         10.5
>  7      2           192          191     11           .         10.5
>  8      2           192          193     11           .         10.5
>
> -----Mensaje original-----
> De: [email protected]
> [mailto:[email protected]] En nombre de Nick Cox 
> Enviado el: jueves, 16 de enero de 2014 12:31
> Para: [email protected]
> Asunto: Re: st: Counting firms in a panel dataset
>
> Sorry, but I am lost here. Clearly I don't have your data and you 
> don't even show your code, nor do I understand in what sense what any 
> code used doesn't work.
>
> As I understand it, you want to identify the 11 observations that 
> appear when 408 are selected but do not appear when 397 are selected.
> I am waving general logic at you, namely that
>
> the complement of A & B in A is A & !B
>
> and you don't identify a fallacy in that.
>
>  What are you showing us? It's not 11 observations.
> Nick
> [email protected]
>
>
> On 16 January 2014 11:10, Miguel A. Duran <[email protected]> wrote:
>> Yes, Nick, I tried something quite similar, and I have just tried 
>> what you propose. If I am not mistaken the reason why it doesn't work 
>> is because
>> -!(var1 == 10/var2 | var1 == 11/var2)- includes observations 1, 2 and
>> 4 for
>> id1 and all observations of id2. Therefore, both agents are taken 
>> into account under -codebook id if...-
>>
>> obs  id     startdate    date   var1      var2       mean_var1
>>    1      1           189          187     10           .
>> 10.75
>>    2      1           189          188     11           .
>> 10.75
>>    3      1           189          189     11           1
> 10.75
>>    4       1           189          190     11           .
>> 10.75
>>    5       2           192          189     10           .
>> 10.5
>>    6       2           192          190     10           .
>> 10.5
>>    7       2           192          191     11           .
>> 10.5
>>    8       2           192          193     11           .
>> 10.5
>>
>> -----Mensaje original-----
>> De: [email protected]
>> [mailto:[email protected]] En nombre de Nick Cox 
>> Enviado el: jueves, 16 de enero de 2014 11:51
>> Para: [email protected]
>> Asunto: Re: st: Counting firms in a panel dataset
>>
>> Did you try it? As I understand it, the complement of
>>
>> A & B
>>
>> in A is
>>
>> A & !B
>>
>> Nick
>> [email protected]
>>
>>
>> On 16 January 2014 10:36, Miguel A. Duran <[email protected]> wrote:
>>> Thanks, Nick, for your answer. I thought of something similar to 
>>> what you propose, but if I am not mistaken it has a problem: I would 
>>> be counting both
>>> id1 and id2, i.e., I would get again 408 (what I get just using 
>>> -codebook id if mean_var1 != 11-).
>>>
>>> id     startdate    date   var1      var2       mean_var1
>>>  1           189          187     10           .               10.75
>>>  1           189          188     11           .               10.75
>>>  1           189          189     11           1              10.75
>>>  1           189          190     11           .               10.75
>>>  2           192          189     10           .               10.5
>>>  2           192          190     10           .               10.5
>>>  2           192          191     11           .               10.5
>>>  2           192          193     11           .               10.5
>>>
>>> -----Mensaje original-----
>>> De: [email protected]
>>> [mailto:[email protected]] En nombre de Nick Cox 
>>> Enviado el: miércoles, 15 de enero de 2014 20:28
>>> Para: [email protected]
>>> Asunto: Re: st: Counting firms in a panel dataset
>>>
>>> I'd look at data that satisfy
>>>
>>> if mean_var1 != 11 & !(var1 == 10/var2 | var1 == 11/var2)
>>>
>>> i.e. negating the second condition. Note that if -var1- and -var2- 
>>> are both missing, then the second condition
>>>
>>> (var1 == 10/var2 | var1 == 11/var2)
>>>
>>> reduces to
>>>
>>> . == .
>>>
>>> which is always true.
>>> Nick
>>> [email protected]
>>>
>>>
>>> On 15 January 2014 19:18, Miguel A. Duran <[email protected]> wrote:
>>>> Hi, Statlisters. I am using -codebook- to count the number of 
>>>> agents in a panel dataset under different criteria. Under a 
>>>> criterion I get
>>>> 408 agents and under another one I get 397. I have an intuition 
>>>> about the cause of this difference and I would like to check it 
>>>> out, but I do
>>> not know how to do it.
>>>> To help make clear my point, (the relevant part of) my dataset 
>>>> looks similar to this,
>>>>
>>>> id     startdate    date   var1      var2       mean_var1
>>>> 1           189          187     10           .               10.75
>>>> 1           189          188     11           .               10.75
>>>> 1           189          189     11           1              10.75
>>>> 1           189          190     11           .               10.75
>>>> 2           192          189     10           .               10.5
>>>> 2           192          190     10           .               10.5
>>>> 2           192          191     11           .               10.5
>>>> 2           192          193     11           .               10.5
>>>>
>>>> Using the command -codebook id if mean_var1 != 11- I get 408 
>>>> agents, but using the command -codebook id if mean_var1 != 11 & 
>>>> (var1 ==
>>>> 10/var2 | var1 == 11/var2)- I get 397 agents. My intuition is that 
>>>> this happens because there are agents (like agent 2) that do not 
>>>> have the observation corresponding to the startdate. If I am right 
>>>> adding this requirement to the command -codebook id if mean_var1 !=
>>>> 11- should count 11 agents, but I do not know how to include that
>> requirement.
>>> Will anyone please help with this?

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