Solved
SAS Employee
Posts: 268

# Interactions in factorial design

Hi - I can specify a full factorial model with factors A, B, C and D in PROC GLM, PROC GLMSELECT etc using notation like this: A | B | C | D.  But can I tell the procedure that I only want to include interactions of A, B, C and D upto and including the second order?  Obviously I could write them all out in full (A*B  A*C A*D B*C etc), but I'm guessing there's probably an easier way.  Is there?

Many thanks.

Accepted Solutions
Solution
‎08-31-2012 08:00 AM
Posts: 2,655

## Re: Interactions in factorial design

There sure is.  For your situation, use A|B|C|D@2.  This will give a model with main effects and all two way interactions.  In the documenation for GLM, look at Example 42.11 Analysis of a Screening Design, where they present a four factor model, and fit main effects and the two way interactions.

Steve Denham

All Replies
Solution
‎08-31-2012 08:00 AM
Posts: 2,655

## Re: Interactions in factorial design

There sure is.  For your situation, use A|B|C|D@2.  This will give a model with main effects and all two way interactions.  In the documenation for GLM, look at Example 42.11 Analysis of a Screening Design, where they present a four factor model, and fit main effects and the two way interactions.

Steve Denham

SAS Employee
Posts: 268

## Re: Interactions in factorial design

Posted in reply to SteveDenham

Perfect - just what I needed.

Many thanks!

🔒 This topic is solved and locked.

Need further help from the community? Please ask a new question.

Discussion stats
• 2 replies
• 205 views
• 0 likes
• 2 in conversation