Date:         Sat, 14 Jun 2008 23:36:25 GMT
Reply-To:     Lou <lpogoda@VERIZON.NET>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Lou <lpogoda@VERIZON.NET>
Subject:      Re: SAS operation generating missing values
Comments: To: sas-l@uga.edu

"sphinx0101" <sphinx0101@gmail.com> wrote in message
news:fe8657f3-eb0c-4d56-8d70-79808c9a42b4@25g2000hsx.googlegroups.com...
> On Jun 14, 5:13 pm, hs AT dc-sug DOT org ("Howard Schreier)" wrote:
> > On Sat, 14 Jun 2008 13:12:03 -0700, sphinx0101 <sphinx0...@GMAIL.COM>
wrote:
> > >Hi All,
> > >I am running into a strange problem with SAS. I imported this excel
> > >file into SAS without any problem. Now when I am running an operation
> > >I am getting missing values for the first observation. I created a
> > >simple dataset which helped me to see the nature of the problem as
> > >follows
> >
> > >x       y
> > >10     5
> > >20     2
> > >30     4
> > >40     8
> >
> > >Now when I am trying to create a simple varible z = x/y I am getting
> > >the following
> >
> > >x       y        z
> > >10     5        .
> > >20     2       2
> > >30     4       10
> > >40     8       7.5
> >
> > >As you can see the problem is that SAS is doing the calculation and
> > >entering the new variable value with respect to the second
> > >observation. I am not sure why this is happening. Any help would be
> > >greatly acknowledged.
> >
> > Any help is unlikely, unless you post your code.
>
> I am sorry. My code was
>
> data new;
> z = x/y;
> set mylib.new;
> run;
>
> I am not sure why this problem occured, as you can see this was a
> simple exercise.

Apparently not as simple as you think.  The first time the calculation is
made, you haven't read any data yet, so x is missing, y is missing, and of
course z will be missing.  And that's what gets written to the output
dataset.  The second time the calculation executes, you're working with data
from the first observation, so z is correctly calculated as 2.  Then you
read in the second observation and write the output.

To correct the situation the SET statement should come before the "z=x/y"
statement.