Date:         Fri, 25 Jun 2004 12:20:23 +0200
Reply-To:     Erik Christiansen <ec@SELVMORDSFORSKNING.DK>
Sender:       "SAS(r) Discussion" <SAS-L@LISTSERV.UGA.EDU>
From:         Erik Christiansen <ec@SELVMORDSFORSKNING.DK>
Organization: UNI-C
Subject:      phreg and var1*var2 (interaction variables)

Hi
I am working with proc phreg in a case/control design. I would like to
analyse interaction between to variabls. I have the total of 20 variables in
my analyse, and this will result i many interaction variables. One varibel
can interact with the rest 19 varibles. I am only interested in significant
interaction variables. Is there an easy way to define the interaction
variables? It is possible to define them in a data statment as
INTER_VAR1_VAR2=VAR1*VAR2;
but this includes a lot of work. Is it possible to do this in the proc phreg
statment, maby like:

proc phreg data=XXX;
  strats ID;
  model Y = VAR1 VAR2 VAR3 (and all significant interaction variables with
degree of 2);
run;
 thanks Erik, Denmark