st: add up variable / quantile

["Scharnigg, Stan (Stud. SBE)" <s.scharnigg@student.maastrichtuniversity.nl>]

Hello,

Thank you for time. I have two questions:
A. I want to know the performance of retail investors. I have the account IDs, but the data
is seperated in months. So I merged the files into stata. However, now I have multiple account IDs and Stata recognizes the performance for every month.
I want to know what the total performance is for a single account ID. 

I will give a short example to make clear what I mean:

accountID; gross_performance
1                -.1
1                 .2
3                 .1
3                 .1

desired outcome:
AccountID; gross_performance 
1                 .1 (-.1+.2)
3                 .2 (.1+.1)


B. Then, when I have the total performance. I want to divide it into quantiles (I want to get the top 25 percentile)
If I use this command:
"xtile quanvariable = Gross_performance, nquantiles(4)"
I create a new variable and the top 25 percentile gets the number 4.  However, how do I get an overview which account IDs are in the top 25 percentile? 
There will be around 2500 observations in the top 25 percentile, so therefore I was hoping that there is an option to get this information in an overview. 

Thank you for your answer

Stan
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