Date:         Wed, 16 Jan 2008 03:34:19 -0500
Reply-To:     Richard Ristow <wrristow@mindspring.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
Comments:     RFC822 error: <W> MESSAGE-ID field duplicated. Last occurrence
              was retained.
From:         Richard Ristow <wrristow@mindspring.com>
Subject:      Re: drawing samples for hundreds of workers
Comments: To: "Raffe, Sydelle, SSA" <DRaffe@acgov.org>
Comments: cc: King Douglas <king_d@swbell.net>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 08:33 PM 1/14/2008, Raffe, Sydelle, SSA wrote:

>In my file, there are unique case records. These are apportioned to
>hundreds of different workers such that each worker has multiple cases.
>
>We want to make a random selection of each workers cases. I don't
>think that's what I led [John Norton] to understand.


And at 01:40 PM 1/15/2008, Raffe, Sydelle, SSA wrote:

>Actually, we want 6 cases randomly selected for each worker.

King Douglas gave a nice implementation using SORT CASES and RANK. As
an alternative, here's the implementation with AGGREGATE and 'k/n'
logic. (It requires that the file be grouped, but not necessarily
sorted, by ID.) I'm selecting three records per worker.

|-----------------------------|---------------------------|
|Output Created               |16-JAN-2008 03:32:16       |
|-----------------------------|---------------------------|
ID   Fname    Lname           RecdDate

A35  Aaron    Aardvark     18-DEC-2004
A35  Aaron    Aardvark     25-MAY-2005
A35  Aaron    Aardvark     16-JUL-2005
A42  Bethany  Birkinwell   30-OCT-2004
A42  Bethany  Birkinwell   05-DEC-2004
A42  Bethany  Birkinwell   24-DEC-2004
A42  Bethany  Birkinwell   25-DEC-2004
C19  Charles  Cubbage      25-JUL-2003
C19  Charles  Cubbage      02-SEP-2003
C21  Dorothy  Dickens      14-NOV-2002
D98  Ellis    Etheridge    19-SEP-2000

Number of cases read:  11    Number of cases listed:  11


AGGREGATE OUTFILE=* MODE=ADDVARIABLES
    /BREAK=ID
    /NRecords 'Number of records for employee'=NU.

NUMERIC   #K #N (F3).

DO IF   $CASENUM EQ 1
      OR ID       NE LAG(ID).
.  COMPUTE #N = NRecords  /* Total records,    per worker  */.
.  COMPUTE #K = MIN(3,#N) /* Number to sample, per worker  */.
END IF.

.  /*-- PRINT  / 'Record ' ID Fname Lname RecdDate ': ' /*-*/
    /*--          'K=' #K ', N=' #N                      /*-*/.

COMPUTE #Take_It = RV.BERNOULLI(#K/#N).
COMPUTE #K = #K - #Take_It.
COMPUTE #N = #N - 1.

.  /*-- PRINT  / '       TAKE=' #Take_It                /*-*/.

SELECT IF #Take_It.

.  /*-- EXECUTE                                         /*-*/.

LIST.

List
|-----------------------------|---------------------------|
|Output Created               |16-JAN-2008 03:32:17       |
|-----------------------------|---------------------------|
ID   Fname    Lname           RecdDate NRecords

A35  Aaron    Aardvark     18-DEC-2004        3
A35  Aaron    Aardvark     25-MAY-2005        3
A35  Aaron    Aardvark     16-JUL-2005        3
A42  Bethany  Birkinwell   30-OCT-2004        4
A42  Bethany  Birkinwell   05-DEC-2004        4
A42  Bethany  Birkinwell   25-DEC-2004        4
C19  Charles  Cubbage      25-JUL-2003        2
C19  Charles  Cubbage      02-SEP-2003        2
C21  Dorothy  Dickens      14-NOV-2002        1
D98  Ellis    Etheridge    19-SEP-2000        1

Number of cases read:  10    Number of cases listed:  10
===================
APPENDIX: Test data
===================
*  ................................................................. .
*  .................   Test data               ..................... .
SET RNG = MT       /* 'Mersenne twister' random number generator  */ .
SET MTINDEX = 3605 /*  Providence, RI telephone book              */ .


INPUT PROGRAM.
.  DATA LIST LIST
           /ID Fname Lname
           (A4,A8,   A12).
.  LEAVE   ID Fname Lname.
.  NUMERIC    RecdDate (DATE11).
.  LEAVE      RecdDate.
.  COMPUTE    RecdDate=RV.UNIFORM(DATE.MDY(01,01,2000),
                                  DATE.MDY(01,01,2005)).
.  COMPUTE    RecdDate=XDATE.DATE(RecdDate).

.  NUMERIC    #NRecrds #RecdNum (F3).
.  COMPUTE    #NRecrds = TRUNC(RV.UNIFORM(1,5)).
.  LOOP       #RecdNum = 1 TO #NRecrds.
.     COMPUTE RecdDate = RecdDate + RV.EXP(1/TIME.DAYS(45)).
.     COMPUTE RecdDate=XDATE.DATE(RecdDate).
.     END CASE.
.  END LOOP.
END INPUT PROGRAM.

BEGIN DATA
A35  Aaron   Aardvark
A42  Bethany Birkinwell
C19  Charles Cubbage
C21  Dorothy Dickens
D98  Ellis   Etheridge
END DATA.

LIST.

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