Folks:
 
I'm having trouble doing a forward variable selection using step()
 
First, I fit an initial model:
 
fit0  <-  glm ( est~1 , data=all, subset=c(n>=25) )
 
then I invoke step():
 
fit1 <- step( fit0 , scope=list(upper=est~ pcped + pchosp + pfarm
,lower=est~1))
 
 
I get the error message:  Error in eval(expr, envir, enclos) : invalid
'envir' argument
 
I looked at the documention on step(). There is no 'envir' arguement.
 
Can anyone shed light on what I'm doing wrong? 
 
Thanks,
Phil Smith
CDC

 


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