[R] need help with understanding stepAIC

From: Bala Thanigaivelan <bala.thanigaivelan_at_veitchlister.com.au>
Date: Thu, 03 Apr 2008 12:21:40 +1000


Hi,  

I am currently using R extensively to develop a statistical model and currently learning its capabilities.

I am trying to develop a logistic regression model using glm and stepAIC  

I constructed my formula as y ~ a + b + c + d

Now I wish to study the interaction between variables. So I did y ~ a + b + c:d + d  

The software generated the coefficients for a, b , c:d, d  

Now I want to compute the probability for various events using the logistic regression model formula  

  Prob = exp(y)/(1+exp(y))  

How do I compute the value of y for the formula with interaction variables ? what does c:d represent given a dataset ?  

Regards,  

Balavelan

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