Re: st: Need Help with Stata Programming

[Nick Cox <njcoxstata@gmail.com>]

<>

You already know the basics here. Irregularity of dates does not bite
for this problem.

bysort id location (visitdate) : gen when_2_1 = visitdate[1] if location == 2

bysort id location (visitdate) : gen when_2_2 = visitdate[2] if location == 2

Nick
njcoxstata@gmail.com


On 7 January 2014 07:00, Michael Stewart <michaelstewartresearch@gmail.com>

> 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
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