Date:         Wed, 12 Mar 2003 00:30:38 GMT
Reply-To:     julierog@ix.netcom.com
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Roger Lustig <trovato@BELLATLANTIC.NET>
Subject:      Re: grouping and creating datasets
Content-Type: text/plain; charset=us-ascii; format=flowed

Dear Leyla:
You seem to be almost there.  Try this:

data
increase
decrease
flat
mixed
;
set grades;
by student;
retain oldgrade;
if first.student then do;
   increase=0; decrease=0;
   end;
else do;
   *** German-style grades: 1 is best;
   *** Don't try this in Switzerland!;
   if grade < oldgrade then increase + 1;
   else if grade > oldgrade then decrease + 1;
   ***Assumes that every student has 2 or more grades;
   ***Also assumes that you want only one record per student;
   if last.student then do;
     if increase and decrease then output mixed;
     else if decrease then output decrease;
     else if increase then output increase;
     else output flat;
     end;
   end;
oldgrade=grade;
keep student;
run;

This can be done more elegantly with a DOW-loop, of course.

Best,

Roger Lustig

leyla yerlikaya wrote:
> Hello all,
>
> I would like to create four different datasets. One of the datasets
> includes all of the students whose grades only improved over the time
> (dataset 1). The other one will include all of the students whose grades
> decreased (dataset 2), another one will include all the students whose
> records stayed the same (dataset 3), and the last one will include the
> students whose grades both increased and decreased.
>
> For instance, if I use the following sample dataset student A should be
> in the dataset1, student B should be in the dataset 3, student C should
> be in the dataset 2, and the student D should be in the dataset 4.
>
> Student     Grade
>
> A                5
>
> A                3
>
> A                3
>
> B                4
>
> B                4
>
> B                4
>
> B                4
>
> C                3
>
> C                5
>
> C                5
>
> D                5
>
> D                4
>
> D                5
>
> D                4
>
> D                5
>
> I wrote a code that calculates the 'difference' of the first and second,
> second and the third, ... grades for each student. I also generated
> dummy variables using this 'difference' variable which help to
> understand if that grade increased or decreased.
>
> Now my dataset looks like this:
>
>
>
> Student     Grade  difference   increase     decrease   nochange
>
> A                5           -2             0
> 1                0
>
> A                3            0             0
> 0               1
>
> A                3           .
>
> B                4          0                0
>  0                1
>
> B                4          0                0
> 0                 1
>
> B                4          0
> 0                0                 1
>
> B                4           .
>
> C                3         +2               1
> 0                  0
>
> C                5           0               0
> 0                   0
>
> C                5            .
>
> D                5            -1            0
> 1                 0
>
> D                4
> +1           1                0                 0
>
> D
> 5            -1           0                1                 0
>
> D                4
> +1            1                0                 0
>
> D                5             .
>
>
>
> I will appreciate if you could give me a couple of hints on creating my
> datasets after this point.
>
>
>
> Thanks,
>
> leyla
>
>
>
>
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>
>
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