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# Re: st: calculating cumulative values of other observations

 From Eric Booth To statalist@hsphsun2.harvard.edu Subject Re: st: calculating cumulative values of other observations Date Fri, 6 Apr 2012 20:29:36 -0500

```<>

******************!

//input example data//
clear
inp ID	str18 date  str4 activity hours
1	20071230  A	10
1	20071122  A	11
2	20071120  A	5
3	20071210  B	6
3	20071111  B	24
3	20071130  F	20
3	20070511  B	49
4	20070611  A	50
end

//cleanup//
g date2 = date(date, "YMD")
format date2 %td
sort ID activity date2

//gen prior hours var//
g priorhrs = 0
forval n = 1/`=_N' {
by ID activity: replace priorhrs =  ///
priorhrs + hours[_n-`n']  ///
if date2[_n]>=date2[_n-`n']
}
l
********************!

- Eric

__
Eric A. Booth
Public Policy Research Institute
Texas A&M University
ebooth@ppri.tamu.edu
+979.845.6754

On Apr 6, 2012, at 6:09 PM, KOTa wrote:

> Hi all,
>
> i have a data looking like this:
>
> ID	date	            activity	hours prior	     result should be:
> 1	20071230  	A	10	   ?	<--	11
> 1	20071122	        A	11	   ?		0
> 2	20071120	        A	5	   ?		0
> 3	20071210	        B	6	   ?		73
> 3	20071111	        B	24	   ?		49
> 3	20071130	        F	20	   ?		0
> 3	20070511	        B	49	   ?		0
> 4	20070611	        A	50	   ?		0
>
> (better picture here http://gyazo.com/5dc1218534d8b185ab22989069034b8a.png )
>
> i need to fill "prior" column with following:
> - amount of hours spent on same activity by same user(ID) prior to
> date of current activity.
>
> example:
> in case of observation 4(line 4) activity is B, so prior = sum of
> hours spent on activity B before it took place (i.e. before 20071210)
> there are 2 such observations, one with 49 hour, another with 24.
> Therefore, prior = 24+49=73.
>
>
> any suggestions how to make this simple?
>
> i was thinking to use "sort" and "by:", but i can't figure out how to
> conditionally("if")  sum up values from different observations into
> "prior" var
> its not a first time i encounter similar problem and always took some
> way around, but this time i decided to ask, maybe there is proper,
> simple way to do this
>
> thank you in advance
>
> K.
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```