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# Re: st: Difference of values in the same column/variable

 From Gokhan Yilmaz To statalist@hsphsun2.harvard.edu Subject Re: st: Difference of values in the same column/variable Date Thu, 24 Nov 2011 17:32:28 -0500

```Thanks a lot for the ideas Anna and Tirthankar. i was trying your
suggestions and this came to my mind and it solved the issue:

replace ewdiffret=. if ewdiffret==0  // I would get so many 0 values
for a reason i do not know.
egen ewmax=max(ewdiffret), by(t)
replace ewdiffret= -1*ewmax

Best,

Gokhan

On Wed, Nov 23, 2011 at 9:37 PM, Tirthankar Chakravarty
<tirthankar.chakravarty@gmail.com> wrote:
> You have a panel setup and for error-free handling in cases like this,
> use Stata's -xt- machinery:
>
> *****************************************
> clear*
> input group  str7 time    ewportret
> 1       2007m4  .0375245
> 1       2007m5  .0397919
> 1       2007m6  -.0188678
> 0       2007m4  .041679
> 0       2007m5  .0449738
> 0       2007m6  -.0240277
> end
> g time2 = monthly(time, "YM")
> format time2 %tm
> xtset group time2
> g dewportret = D.ewportret
> li
> *****************************************
> T
>
> On Wed, Nov 23, 2011 at 6:23 PM, Anna Reimondos <areimondos@gmail.com> wrote:
>> Hi Gokhan
>> Maybe something like
>>
>>
>> gen newvar=.
>> gsort time -group
>> bysort time: replace newvar=ewportret-ewportret[_n+1] if group==1 &
>> group[_n+1]==0
>>
>> Or in a loop
>>
>> gen newvar=.
>> forvalues n=1/6 {
>> replace newvar=ewportret-ewportret[`n'] if time==time[`n'] & group==1
>> }
>>
>>
>> Anna
>>
>>
>> On Tue, Nov 15, 2011 at 1:21 PM,  <yilmag@rpi.edu> wrote:
>>> Dear All,
>>>
>>> How can i create a new variable that is equal to the difference in ewportret
>>> (see below table) between two groups in the same month?
>>> For example: the first row of the newvar below would be equal to (.0375245-
>>> .041679) and the second row would be equal to(.0397919- .0449738)
>>>
>>>
>>> group   time    ewportret  newvar
>>>
>>> 1       2007m4  .0375245
>>> 1       2007m5  .0397919
>>> 1       2007m6  -.0188678
>>> 0       2007m4  .041679
>>> 0       2007m5  .0449738
>>> 0       2007m6  -.0240277
>>>
>>>
>>> Thank you
>>>
>>> Gokhan
>>>
>>>
>>> *
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>>>
>>
>> *
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>>
>
>
>
> --
> Tirthankar Chakravarty
> tchakravarty@ucsd.edu
> tirthankar.chakravarty@gmail.com
>
> *
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>

*
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```