Model Statement in Proc Logistic

[msdinesh87]

Hello,

I have a question regarding the model statement syntax in proc logistic. I read that the below two model statements are equivalent.

1. Mode1 Purchase * Gender Age Region;

2. Mode1 Purchase * Gender|Age|Region @1;

I have never seen such model statements ever before. My questions are

1. Can we use asterisk to separate the dependent from independent variables?

2. What is the @1 doing in the 2nd option above?

3. How are these two statements equivalent?

[Reeza · Accepted solution]

1. No. The asterisk is used to denote interaction terms rather than a single term.

2. The bars | separating the variables tell SAS to consider interaction between those variables, but the @1 says to only consider single level so no interaction. If it was @2 then it would consider all 2 level interactions (Gender*Age Gender*Region Age*Region etc) between the variables. 

3. I don't think they're equivalent.