RE: st: RE: creating variable summarizing for each individual properties of other members of a group at t-1

[Erik Aadland <erikaadland@hotmail.com>]

My apologies if I am being imprecise.
 
I am struggling in my attempt to create the following two variables.
 
One variable that yields a score for each individual in the dataset for each yearmonth: the score is the sum of all ind_entry = 1 for all the other individuals excluding the focal individual up until and including time: yearmonth - 1.
 
And a second variable that identifies for each individual in the dataset for each yearmonth: the total number of other individuals in the dataset that have experienced ind_entry = 1 at least once up until and including time: yearmonth - 1. In this variable, I want to count the number of individuals that have experienced ind_entry = 1, not how many times they have entered.
 
Sincerely,
 
Erik Aadland.


----------------------------------------
> From: n.j.cox@durham.ac.uk
> To: statalist@hsphsun2.harvard.edu
> Date: Tue, 17 May 2011 19:22:50 +0100
> Subject: RE: st: RE: creating variable summarizing for each individual properties of other members of a group at t-1
>
> I naturally have no idea what -ind_entry- means.
>
> I am just summing it, as the code implies. Is that not what you want?
>
> Nick
> n.j.cox@durham.ac.uk
>
>
> -----Original Message-----
> From: owner-statalist@hsphsun2.harvard.edu [mailto:owner-statalist@hsphsun2.harvard.edu] On Behalf Of Erik Aadland
> Sent: 17 May 2011 19:14
> To: statalist@hsphsun2.harvard.edu
> Subject: RE: st: RE: creating variable summarizing for each individual properties of other members of a group at t-1
>
> Thank you so much for your input, Nick.
>
> I have experimented and generated different variables previously relying on the very helpful FAQ in question.
>
> I am struggling with this problem however. When I apply the suggested code below, it appears that the calculation of the number of peers adds up more than it should for ind_ids with more ind_entry = 1 relative to other ind_ids, and consequently contribute more to the "score" than those with fewer ind_entry = 1.
>
> Referring to the example dataset, ind_id 2 is given the correct "prevscore". Ind_id 4, however, is not. By yearmonth 12, ind_id 4 has contributed 2 ind_entry=1 to the "score", which is correct for ind_id 2. However, ind_id 2 has not yet experienced ind_entry=1. Consequently, score - 1 for ind_id 4 yields a score = 1 in yearmonth 11 and 12, when the correct score = 0. And so on.
>
> Here is the suggested code as I applied it:
>
> clear ;
> #delimit ;
> use "ind_entry_ex.dta" ;
> sort yearmonth ;
> gen score = sum(ind_entry) ;
> by yearmonth: replace score = score[_N] ;
> replace score = score - ind_entry ;
> bysort ind_id (yearmonth): gen prevscore = score[_n-1] ;
>
>
> Here is the output:
>
> year month yearmonth ind_id ind_entry score prevscore
> 2003 10 10 2 0 1
> 2003 11 11 2 0 1 1
> 2003 12 12 2 0 2 1
> 2004 1 13 2 0 2 2
> 2004 2 14 2 1 2 2
> 2004 3 15 2 0 3 2
> 2003 10 10 4 1 0
> 2003 11 11 4 0 1 0
> 2003 12 12 4 1 1 1
> 2004 1 13 4 0 2 1
> 2004 2 14 4 0 3 2
> 2004 3 15 4 0 3 3
>
> I use Stata 10.
>
>
> Thanks again and kind regards,
>
> Erik.
>
>
> ----------------------------------------
> > From: n.j.cox@durham.ac.uk
> > To: statalist@hsphsun2.harvard.edu
> > Date: Tue, 17 May 2011 17:47:53 +0100
> > Subject: st: RE: creating variable summarizing for each individual properties of other members of a group at t-1
> >
> > I don't know what "I am familiar with" means here. Does it mean that you've read the FAQ but can't see how to apply it?
> >
> > This sounds to me like
> >
> > 1. Get the sum of all individual entries
> >
> > sort yearmonth
> > gen score = sum(ind_entry)
> > by yearmonth : replace score = score[_N]
> >
> > 2. Subtract this individual
> >
> > replace score = score - ind_entry
> >
> > 3. Look one step back in time
> >
> > bysort ind_id (yearmonth) : gen prevscore = score[_n-1]
> >
> > Nick
> > n.j.cox@durham.ac.uk
> >
> > Erik Aadland
> >
> > I need to create a variable that sums for each individual in my dataset the total number of ind_entry of all other individuals at time: yearmonth - 1.
> > I have attached a small ex of my data structure below. So for instance, given the small dataset below, for ind_id 2 in yearmonth 11 this variable score = 1. But for ind_id 4 in the same yearmonth, the score = 0.
> >
> > I would also like to generate a variable that identifies for each individual the unique number of other individuals in the dataset that have experienced ind_entry = 1 at least once up until time: yearmonth - 1.
> >
> > I am familiar with the following FAQ: http://www.stata.com/support/faqs/data/members.html
> >
> > My data structure is snapshot data in principle like the example below, but some individuals enter the observation window later than others (i.e. in later yearmonths):
> >
> > year month yearmonth ind_id ind_entry
> > 2003 10 10 2 0
> > 2003 11 11 2 0
> > 2003 12 12 2 0
> > 2004 1 13 2 0
> > 2004 2 14 2 1
> > 2004 3 15 2 0
> > 2003 10 10 4 1
> > 2003 11 11 4 0
> > 2003 12 12 4 1
> > 2004 1 13 4 0
> > 2004 2 14 4 0
> > 2004 3 15 4 0
> >
>
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