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Re: st: RE: what command to keep firms-years with multiple occurrence of only one type of events
From
Nahla Betelmal <[email protected]>
To
"[email protected]" <[email protected]>
Subject
Re: st: RE: what command to keep firms-years with multiple occurrence of only one type of events
Date
Wed, 2 Oct 2013 11:49:48 +0100
Thank you so much everyone. You gave me a great help.
Many thanks
Nahla
On 27 September 2013 16:39, Roberto Ferrer <[email protected]> wrote:
> Seems Robert beat me to that one.
>
> Bests,
> Roberto
>
> On Fri, Sep 27, 2013 at 4:37 PM, Roberto Ferrer <[email protected]> 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 <[email protected]> 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 <[email protected]> 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: [email protected] [mailto:[email protected]] On Behalf Of Nahla Betelmal
>>>> Sent: Friday, September 27, 2013 4:43 AM
>>>> To: [email protected]
>>>> 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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>>>
>>> *
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>
> *
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