At 11:37 AM 10/28/2007, David Wright wrote:
>I need to select cases from a specific date/program forward in
>time. Listed below is the data layout. [As SPSS 14 LIST output;
>modified, adding variable RecdNum.]
|-----------------------------|---------------------------|
|Output Created |28-OCT-2007 13:55:38 |
|-----------------------------|---------------------------|
[TestData]
RcrdNum caseid year program
001 1 2001 A
002 1 2003 A
003 1 2004 B
004 1 2005 B
005 2 2003 A
006 2 2004 B
007 2 2005 A
008 3 2001 B
Number of cases read: 8 Number of cases listed: 8
>I would need to select cases when the subjects "started" program B &
>any following years. Notice in case #2 I would need the last 2
>records.
>
>I thought perhaps a lag fucntion here to denote when program B starts
>might work but confused in case #2.
Selecting cases using LAG is notoriously tricky, but this instance
seems straightforward. I believe the following gives what you want.
It's SPSS 14 draft output (WRR:not saved separately). The dataset's
called "NaiveLag", because I was afraid I'd have trouble and have to
code a more elaborate alternative.
DATASET ACTIVATE NaiveLag.
SELECT IF program EQ 'B'
OR caseid EQ LAG(caseid).
LIST.
List
|-----------------------------|---------------------------|
|Output Created |28-OCT-2007 14:09:08 |
|-----------------------------|---------------------------|
[NaiveLag]
RcrdNum caseid year program
003 1 2004 B
004 1 2005 B
006 2 2004 B
007 2 2005 A
008 3 2001 B
Number of cases read: 5 Number of cases listed: 5
===================
APPENDIX: Test data
===================
* ................................................................. .
* ................. Test data ..................... .
INPUT PROGRAM.
. NUMERIC RcrdNum (N3).
. LEAVE RcrdNum.
. COMPUTE RcrdNum = RcrdNum + 1.
. DATA LIST FREE / caseid year program
(F2, F4, A2).
END INPUT PROGRAM.
BEGIN DATA
1 2001 A
1 2003 A
1 2004 B
1 2005 B
2 2003 A
2 2004 B
2 2005 A
3 2001 B
END DATA.
DATASET NAME TestData.
LIST.
DATASET COPY NaiveLag.
DATASET COPY Execute.
DATASET COPY Involved.
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