Note that the approach behind Martin's suggestion is elaborated in
excruciating detail in an FAQ:
FAQ . . . . . . . . . . . . . . . First and last occurrences in
panel data
3/07 How can I identify first and last occurrences
systematically in panel data?
<http://www.stata.com/support/faqs/data/firstoccur.html>
That FAQ is closely aligned with another:
FAQ . . . . . . . . . . . . . . . . . . Dropping spells of missing
values
3/07 How can I drop spells of missing values at the
beginning and end of panel data?
<http://www.stata.com/support/faqs/data/dropmiss.html>
Nick
[email protected]
Martin Weiss
You simply drop the ones where the (running) -sum- of the dummy is still
below 1
***
clear*
input PtID visit stroke str12 ADMSNDT
1 1 0 1-Feb-05
1 2 0 1-Apr-05
1 3 0 19-Apr-05
1 4 0 14-Oct-05
1 5 0 30-Oct-05
1 6 1 18-Nov-05
1 7 0 2-Dec-05
2 1 0 10-May-05
2 2 0 30-Nov-05
3 1 0 8-Nov-05
4 1 1 4-Mar-05
4 2 0 9-Jul-05
4 3 0 15-Sep-05
5 1 0 31-Aug-05
6 1 0 20-Jul-05
6 2 0 3-Oct-05
7 1 1 27-Nov-05
8 1 1 29-Jul-05
8 2 1 18-Oct-05
9 1 0 13-Mar-05
9 2 0 11-Jul-05
9 3 0 6-Sep-05
9 4 0 28-Nov-05
9 5 0 19-Dec-05
10 1 0 29-Mar-05
10 2 0 4-Mar-05
10 3 0 25-Jul-05
11 1 1 10-Dec-05
12 1 1 16-Jan-05
12 2 0 19-Jan-05
12 3 0 22-Feb-05
end
gen date=date(ADMSNDT, "DM20Y")
format date %tdMonth_DD,_CCYY
compress
//before
list, noobs
//drop before stroke
bys PtID (visit): drop if sum(stroke)<1
//after
list , noobs
***
From: "Dr. Dilip K. Pandey" <[email protected]>
> I am working with hierarchical data.
> There are several hospital visit by patients. My outcome of interest
is
> stroke. Patient is diagnosed with stroke in one or other of hospital
> visit. I would like to exclude visits prior to diagnosis of first
stroke
> (index hospitalization) but would keep informations on hospital visit
> after index hospitalization. Example of dataset is below:
>
> Pt.ID visit stroke ADMSN_DT
> 1 1 0 1-Feb-05
> 1 2 0 1-Apr-05
> 1 3 0 19-Apr-05
> 1 4 0 14-Oct-05
> 1 5 0 30-Oct-05
> 1 6 1 18-Nov-05
> 1 7 0 2-Dec-05
> 2 1 0 10-May-05
> 2 2 0 30-Nov-05
> 3 1 0 8-Nov-05
> 4 1 1 4-Mar-05
> 4 2 0 9-Jul-05
> 4 3 0 15-Sep-05
> 5 1 0 31-Aug-05
> 6 1 0 20-Jul-05
> 6 2 0 3-Oct-05
> 7 1 1 27-Nov-05
> 8 1 1 29-Jul-05
> 8 2 1 18-Oct-05
> 9 1 0 13-Mar-05
> 9 2 0 11-Jul-05
> 9 3 0 6-Sep-05
> 9 4 0 28-Nov-05
> 9 5 0 19-Dec-05
> 10 1 0 29-Mar-05
> 10 2 0 4-Mar-05
> 10 3 0 25-Jul-05
> 11 1 1 10-Dec-05
> 12 1 1 16-Jan-05
> 12 2 0 19-Jan-05
> 12 3 0 22-Feb-05
>
>
> There are close to 800,000 hospitalizations to work with. Please
suggest
> macro or stata program to drop observation (hospital visits) prior to
> index hospitalization but not after.
*
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