Re: st: Counting firms in a panel dataset

[Nick Cox <njcoxstata@gmail.com>]

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
njcoxstata@gmail.com


On 15 January 2014 19:18, Miguel A. Duran <maduran@uma.es> 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?
> Thanks in advance.
>
> Miguel.
>
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