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# Re: st: cumulative summation

 From Nick Cox To statalist@hsphsun2.harvard.edu Subject Re: st: cumulative summation Date Tue, 26 Feb 2013 10:23:30 +0000

```Also

bysort group year : keep if _n == _N

On Tue, Feb 26, 2013 at 9:05 AM, Nick Cox <njcoxstata@gmail.com> wrote:
> It works, but does not do what you want. Many solutions, one of which is
>
> egen nties = max(ties), by(group year)
>
>
> Nick
>
> On Tue, Feb 26, 2013 at 8:39 AM, James Bernard <jamesstatalist@gmail.com> wrote:
>> Thanks Nick,
>>
>> I have missing values in my list, so it seems that the command is not
>> working, because it sets many of the values to . (missing).
>>
>> I gave you the simplifies version. In fact, I am using loops and
>> macros to do this
>>
>> Then, instead would it be possible to write a comand that can detect
>> that for firm A in 1990, 2 is the larger one.
>>
>> Alternatively, would it be possible to ask the program to keep only
>> the last observation of every group (a group defined by firm and year)
>>
>> Thanks a gain,
>> James
>>
>>
>> On Tue, Feb 26, 2013 at 3:49 PM, Nick Cox <njcoxstata@gmail.com> wrote:
>>> bysort firm year (ties) : replace ties = ties[_N]
>>>
>>> Nick
>>>
>>> On Tue, Feb 26, 2013 at 7:08 AM, James Bernard <jamesstatalist@gmail.com> wrote:
>>>
>>>> I have used the sum function to calculate a variable in  a panel data.
>>>>
>>>> Firm        Year      ties
>>>> -----------  ----------    -------
>>>> A             1990      1
>>>> A             1990       2
>>>> A             1991       1
>>>> B             1990       0
>>>> B             1990       1
>>>> B             1990        3
>>>> C             1990        0
>>>> C             1991        0
>>>> C             1992        0
>>>>
>>>> The issue is that the variable ties which is the number of ties a firm
>>>> has formed in a year is a cumulative sum of something and, therefore,
>>>> for a company like A the final number of ties in year 1990 should be
>>>> 2. I need the program to write the same number (final value of the
>>>> cumulative sum) instead of 1.
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```