[R] Logistic Regression

[Frank Harrell]

Which statistical principles are you invoking on which to base such analyses?
Frank

Sergio Della Franca wrote:
> 
> Dear R-Helpers,
> 
> I want to perform a logistic regression on my dataset (y).
> 
> I used the following code:
> 
> logistic<-glm(formula="interest_variable"~.,family = binomial(link =
> logit),
> data = y)
> 
> 
> This run correctly.
> Then i want to develop the logistic regression with three different
> method:
> -forward
> -backward
> -stepwise
> 
> I used these procedure:
> forward<-step(logistica,direction="forward")
> backward<-step(logistica,direction="backward")
> stepwise<-step(logistica,direction="both")
> 
> Even these run correctly, but i obtained the same results with the three
> different procedures.
> 
> Then I tought i made some mistakes.
> 
> My question is:
> 
> Is correct what i did?
> Is correct that three different methods return the same results?
> 
> If i made some mistakes, what is the correct method to correctly perform
> the
> three different logistics regression?
> 
> 
> Thank you in advance.
> 
> 
> Sergio Della Franca.
> 
> 	[[alternative HTML version deleted]]
> 
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> 


-----
Frank Harrell
Department of Biostatistics, Vanderbilt University
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