Re: st: RE: what command to keep firms-years with multiple occurrence of only one type of events

[Roberto Ferrer <refp16@gmail.com>]

Seems Robert beat me to that one.

Bests,
Roberto

On Fri, Sep 27, 2013 at 4:37 PM, Roberto Ferrer <refp16@gmail.com> wrote:
> If I understand correctly, the following should work. Just -sort-,
> compare first event with last event and keep the event that interests
> you.
>
> *-------------------------- begin example --------------------------------------
> clear
> input str2 firm year event
> A        1994       2
> A        1994       3
> A        1994       3
> A        1995       1
> A         1995      3
> A         1996       2
> A         1996       4
> A         1996       3
> A          1997       3
> A           1997      3
> A           1998       1
> A            1998       1
> B         1995      3
> B         1996       2
> B         1996       4
> B         1996       3
> end
>
> * what you want
> sort firm year event
> by firm year: keep if event[1] == event[_N] & event == 3
>
> *----------------------- end example -------------------------------------------
>
> On Fri, Sep 27, 2013 at 2:39 PM, Robert Picard <picard@netbox.com> wrote:
>> Another way:
>>
>> bys Firm Year (Event): keep if (Event[1]==Event[_N]) & Event==3
>>
>> Robert
>>
>> On Fri, Sep 27, 2013 at 9:29 AM, Joe Canner <jcanner1@jhmi.edu> wrote:
>>> Nahla.
>>>
>>> If your Event variable is numeric, this should work:
>>>
>>> . bys Firm Year: egen mn=mean(Event)
>>> . bys Firm Year: egen sd=sd(Event)
>>> . keep if mn==3 & sd==0
>>>
>>> This is, admittedly, a little unconventional, but should be pretty efficient.
>>>
>>> Regards,
>>> Joe Canner
>>> Johns Hopkins University School of Medicine
>>>
>>> -----Original Message-----
>>> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Nahla Betelmal
>>> Sent: Friday, September 27, 2013 4:43 AM
>>> To: statalist@hsphsun2.harvard.edu
>>> Subject: st: what command to keep firms-years with multiple occurrence of only one type of events
>>>
>>> Dear Statalist members,
>>>
>>> It would be great if you can let me know what command I can use to keep firms-years with multiple occurrence of only one type of events in my data.
>>>
>>> I have firms-years-events data set. A firm can have multiple entries for the same year if it undertakes certain corporate events . I coded the events as 1,2,3, 4. For example the data looks like this
>>>
>>>
>>> Firm   Year    Event
>>> A        1994       2
>>> A        1994       3
>>> A        1994       3
>>> A        1995       1
>>> A         1995      3
>>> A         1996       2
>>> A         1996       4
>>> A         1996       3
>>> A          1997       3
>>> A           1997      3
>>> A           1998       1
>>> A            1998       1
>>> B
>>> ..
>>>
>>>
>>> I am only interested in studying firm-years where  only event 3 was undertaken (i.e. keep both entries for year 1997 only). In other words, I want to drop firm years where there are a mix of events shown as multiple entries/observations ( years 1994, 1995, 1996) and multiple unique occurrence of event other than 3 (year 1998).
>>>
>>> I understand that I can do it on two stages, first drop  firm-years with mix events, then second stage drop years with unique events other than 3.
>>>
>>> the problem that I  don't know what command should I use to do the first stage ( drop firms-years with multiple entries of multiple events).
>>>
>>> Thank you in advance, I highly appreciate your kind help
>>>
>>> Nahla Betelmal
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>>
>> *
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