Date:         Tue, 13 May 2008 12:05:52 -0400
Reply-To:     Richard Ristow <wrristow@mindspring.com>
Sender:       "SPSSX(r) Discussion" <SPSSX-L@LISTSERV.UGA.EDU>
From:         Richard Ristow <wrristow@mindspring.com>
Subject:      Re: missing values in do if
Comments: To: Keval Khichadia <kkhichadia@yahoo.com>
Comments: cc: Melissa Ives <mives@chestnut.org>
In-Reply-To:  <156336.37718.qm@web45807.mail.sp1.yahoo.com>
Content-Type: text/plain; charset="us-ascii"; format=flowed

At 01:19 PM 5/12/2008, Keval Khichadia wrote:

>[In the following syntax] I get the correct value (1) for LowIncome
>but there are several cases when there are values for num_in_family
>and Fisap_Income where the value should be 0 but I am getting $sysmis
>
>do if num_in_family = 1 & Fisap_Income <= 19600.
>compute LowIncome = 1.
>else if num_in_family = 2 & Fisap_Income <= 26400.
>compute LowIncome = 1.
>else if num_in_family = 3 & Fisap_Income <= 33200 .
>compute LowIncome = 1.
>else if num_in_family = 4 & Fisap_Income <= 40000.
>compute LowIncome = 1.
>else if num_in_family = 5 & Fisap_Income <= 46800.
>compute LowIncome = 1.
>else if num_in_family = 6 & Fisap_Income <= 53600.
>compute LowIncome = 1.
>else if num_in_family = 7 & Fisap_Income <= 60400.
>compute LowIncome = 1.
>else if num_in_family = 8 & Fisap_Income <= 67200.
>compute LowIncome = 1.
>else if num_in_family = $sysmis | Fisap_Income = $sysmis.
>compute LowIncome = $sysmis.
>else.
>compute LowIncome = 0.
>end if.

Your problem is that the final COMPUTE,
>compute LowIncome = 0.
will never be executed.

The value in test
>else if num_in_family = $sysmis | Fisap_Income = $sysmis.
is never 'true', and it's never 'false', either; it's 'missing'. In a
DO IF, if any test returns 'missing', its clause *and all following
clauses* are skipped, with no notification. (Distinguishing between
'false' and 'missing' in tests was one of SPSS's good ideas; treating
'missing' this way in DO IF, and just like 'false' everywhere else,
was one of the bad ones.)

"SYSMIS" is not a value, so nothing can be equal to it.

You want,

else if SYSMIS(num_in_family) | SYSMIS(Fisap_Income).
compute LowIncome = $sysmis.
else.
compute LowIncome = 0.
end if.

=====================
To manage your subscription to SPSSX-L, send a message to
LISTSERV@LISTSERV.UGA.EDU (not to SPSSX-L), with no body text except the
command. To leave the list, send the command
SIGNOFF SPSSX-L
For a list of commands to manage subscriptions, send the command
INFO REFCARD