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Re: st: calculating cumulative values of other observations


From   KOTa <kota.alba@gmail.com>
To   statalist@hsphsun2.harvard.edu
Subject   Re: st: calculating cumulative values of other observations
Date   Sat, 7 Apr 2012 17:49:20 -0400

ouch, you are so right with idea to split code into 2 parts.
that is the simplest way to do what i want. i guess i just needed fresh eyes.

thank again.

El día 7 de abril de 2012 17:36, Eric Booth <eric.a.booth@gmail.com> escribió:
> <>
>
> Your new [if] condition is preventing the adapted version of Nick's code from creating the running sum properly.  To see how the [if] condition you added is "filtering" the observations that are eligible for the running sum, create an indicator/flag for your [if] conditions and inspect the results:
> ***
>  bysort ID activity (date_start): gen ind = 1 if ///
>        (date_start>=date_end[_n-1] & !mi(date_end[_n-1]))
> ***
>
> You should be able to see that this stops Stata from including the observations you wanted included in the sum using 'ind'.
>
> Without seeing your new variables - you could probably break your new code into two steps like:
> ***
>  bysort ID activity (date_start): gen priorhrs = ///
>        sum(hours) - hours
>  replace priorhrs = 0 if  priorhrs>0 & ///
>        (date_start<date_end[_n-1] & !mi(date_end[_n-1]))
> ***
> to get what you need.
>
> - Eric
> __
> Eric A. Booth
> Public Policy Research Institute
> Texas A&M University
> ebooth@ppri.tamu.edu
> +979.845.6754
>
> On Apr 7, 2012, at 4:12 PM, KOTa wrote:
>
>> thanks Eric,
>> i did adapt your code for real dataset without problems (see my
>> previous response)
>>
>> i am just interested how to do it using Nick's code, which works much
>> faster (dataset is pretty large).
>> i am probably missing some thing about how "sum" works or about
>> boundary conditions
>>
>> my rewrite of Nick was:
>>
>> bysort ID activity (date_start): gen priorhrs = sum(hours) - hours if
>> (date_start>=date_end[_n-1] & !mi(date_end[_n-1]))
>>
>> which does not work :/
>>
>> regards
>> K.
>>
>> El día 7 de abril de 2012 14:09, Eric Booth <eric.a.booth@gmail.com> escribió:
>>> <>
>>>
>>> On Apr 7, 2012, at 9:42 AM, KOTa wrote:
>>>
>>>> thanks Erik, Nick
>>>>
>>>> both ways work on this sample, and i managed to adjust for a real database also.
>>>>
>>>> few followup question:
>>>>
>>>> 1. Eric, any specific reason why you convert time into date format? I
>>>> used it without conversion and it looks fine.
>>>> Also on real data your solution somehow goes into infinite loop after
>>>> finishing all calculations.
>>>>
>>> I don't know how you edited the code, so I don't know how you produced an infinite loop?  It certainly doesn't do that with the example I gave you.  Also, I created a time/date format version of "date" just out of habit, I find that it makes data management easier.  If you don't need/want it, then skip it.
>>>
>>>
>>>> 2. Nick, the solution you proposed with "sum" was the one i tried
>>>> initially. The problem is that in real data I have 2 columns for date
>>>> (start_date end_date) and i want to compare start_date [_n] >=
>>>> end_date[all previous]
>>>> Eric's solution works longer, but i could adjust it to work with
>>>> different date columns.
>>>> your solution is works much faster in case there is one date column,
>>>> but i could not figure out how to do the same with 2 different
>>>> columns.
>>>
>>> El día 7 de abril de 2012 04:08, Nick Cox <njcoxstata@gmail.com> escribió:
>>>> Why not
>>>> bysort id activity (time): gen priorhrs = sum(time) - time
>>>> Nick
>>>
>>>
>>> Nick's -sum- solution does work (and is more straightforward than my -replace line)  with a slight tweak - changing the first "time" to "date2" (if you create the time/date var from my example).  Also, if you are using the same variable names from your original example you'd change "time" to "hours".  Adding this to my example works:
>>>
>>>  bysort ID activity (date2): gen njc = sum(hours) - hours
>>>
>>>
>>> Adapting mine and Nick's code to your "real" dataset is another issue completely - if you cannot figure how to adapt our tips to your data/code, then you should post a data & code example/question that is closer to reality.
>>>
>>>
>>> - Eric
>>> __
>>> Eric A. Booth
>>> Public Policy Research Institute
>>> Texas A&M University
>>> ebooth@ppri.tamu.edu
>>> Office: +979.845.6754
>>>
>>>
>>>
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