Date:         Thu, 31 Oct 2002 13:16:42 -0600
Reply-To:     "Marks, Jim" <jim.marks@lodgenet.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         "Marks, Jim" <jim.marks@lodgenet.com>
Subject:      Re: Why does (missing value) multiplied by zero = zero?
Content-Type: text/plain; charset="iso-8859-1"

Does this help?

** original data-- one case changed to q = 9999 and type = 1.
DATA LIST LIST /TYPE Q.
BEGIN DATA
1 25
1 2
1 0
1 9999
1 17
2 9999
2 26
2 9999
2 0
2 18
END DATA.
LIST.
MISSING VALUES Q (9999).

** new syntax.
COMPUTE qa = q.
DO IF type = 1.
RECODE qa (SYSMIS = -9).
ELSE.
RECODE qa (ELSE = SYSMIS).
END IF.

COMPUTE qb = q.
DO IF type = 2.
RECODE qb (SYSMIS = -9).
ELSE.
RECODE qb (ELSE = SYSMIS).
END IF.

LIST.

HTH

Jim Marks
Senior Market Analyst
LodgeNet Entertainment Corporation
605.988.1616

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-----Original Message-----
From: Andrew Fenyo [mailto:A.J.Fenyo@ukc.ac.uk]
Sent: Thursday, October 31, 2002 11:27 AM
To: SPSSX-L@LISTSERV.UGA.EDU
Subject: Why does (missing value) multiplied by zero = zero?


Folks,

I have been tearing my hair out, but I cannot see what I am doing wrong!

I have a variable Q and a category TYPE. I need to create two new
variables (QA and QB) which take the value of Q  or MISSING depending
on TYPE. It works fine EXCEPT when Q is zero: then I get both QA and QB set
to zero.

I have probably overlooked something very simple, but any suggestions would
be most welcome.

Here is a sample and the syntax:

DATA LIST LIST /TYPE Q.
BEGIN DATA
1 25
1 2
1 0
1 6
1 17
2 6
2 26
2 9999
2 0
2 18
END DATA.
LIST.
MISSING VALUES Q (9999).
COMPUTE ATYPE=2-TYPE.
COMPUTE BTYPE=1-ATYPE.
MISSING VALUES ATYPE BTYPE (0).
LIST.
DO IF MISSING (Q).
COMPUTE QA=-9.
COMPUTE QB=-9.
ELSE.
COMPUTE QA=Q*ATYPE.
COMPUTE QB=Q*BTYPE.
END IF.
MISSING VALUES QA QB (-9).
LIST.

==============================
Andrew Fenyo, Senior Computing Officer
Personal Social Services Research Unit
University of Kent, Canterbury, CT2 7NF
Voice: 01227 827610  Fax: 01227 827038
PSSRU: http://www.ukc.ac.uk/PSSRU