st: data management questions

[David Bai <db555@mail.com>]

Dear all,

    I have two questions regarding data management, and would 
appreciate it if anybody can help.

(1) If I have a datafile like this:

ID(individual id)         NID(neighborhood id)
1                                   100
2                                   100
3                                   104
4                                   102
5                                   104

How can I create a datafile for neighborhood ID variable like this?:
NID
100
102
104

(2) Now since I have the complete list of NIDs (suppose there are 100 
neighborhoods), I'd like to use this NID file to merge with another 
data file (dataset Two, which has neighborhood ID variable and 
time-varying variables. Dataset Two has 200 neighbors) like this:
NID                year              var1
100                1                   850
100                2                   600
101                1                   90
102               1                   600
102                2                  400
103                1                  500
103                2                  400
103                3                  506


 I only want to keep the 100 neighborhoods that appear in the NID file, 
What syntax I can use to merge the two data files for the 100 
neighbors? Thank you very much.

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