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st: Need Help with Stata Programming


From   Michael Stewart <[email protected]>
To   statalist <[email protected]>
Subject   st: Need Help with Stata Programming
Date   Tue, 7 Jan 2014 02:00:26 -0500

Hello ,

I have a question regarding lists and have read Nick's paper on lists
and counting irregularly spaced intervals.

I posted a similar, but different question
http://www.stata.com/statalist/archive/2013-11/msg00882.html
previously.

My dataset is as follows

***********DATASET-BEGIN**************************
ID              VISITDATE        EVENT             LOCATION
1                   Jan_1           May_1                   1
1                   Jan_4          May_1                   2
1                   Jan_6          May_1                   1
1                   May_5         May_1                   1
1                   May_8         May_1                   2
2                   Feb_2         Feb_9                    2
2                   Feb_6         Feb_9                    2
2                   Feb_15         Feb_9                  1
2                   Feb_27         Feb_9                  2
2                   Mar_30         Feb_9                   2

***********DATASET_END****************************


MY NEED:  I am trying to generate the following two variables and
looking to see if the programmers in the statalist may help me.

1) ***** for this variable, can you suggest an shorter/more elegant ********

VAR_1: this varaible shows VISITDATE when the LOCATION was the first
"2" [this is somewhat easier]
Ex:
For patient 1(ID=1), visit date corresponding to first 2 (in location)
would be Jan 4
For patient 2(ID=2), visit date corresponding to first 2 (in location)
would be Feb 2

*************code begin*******************
bysort ID  (VISITDATE): gen VAR_1=VISITDATE if LOCATION==2
bysort ID (VAR_1): gen LOCATION_FIRST2=VAR_1[1]
************code end************************

2)**********I do not know how to generate the following variable
******************

VAR_2: this variable shows VISITDATE  when the LOCATION is the second 2

Ex:
For patient 1(ID=1), visit date corresponding to second 2 (in
location) would be May 8
For patient 2(ID=2), visit date corresponding to second 2 (in
location) would be Feb 6

Thank you very much for your time and consideration.

-- 
Thank you ,
Yours Sincerely,
Mike.
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