I'm attempting to select a model using stepAIC.  I want to use a forward
selection procedure.  I have specified a "scope" option, but must not be
understanding how this works.  My results indicate that the procedure begins
and ends with the "full" model (i.e., all 17 independent variables)...not
what I expected.  Could someone please point out what I'm not understanding?
My code is below.

 

Thanks.

 

Marc

 

> m1.stepFwd <- stepAIC(m1, direction="forward",

+                       scope=list(upper=~age.refc.fo + dusz.cat.fo +

+                         ed.du.f + emp.ref.f + geodist3.f + has.fone.f +

+                         healthdu.f + help.du.f + inc.ref.f + maj.act.f +

+                         marryref.f + msa.stat.f + regionrf.f + r.e.ref.f +

+                         sex.ref.f + type.psu.f + urb.stat.f, lower=~1))

Start:  AIC= 4752.19 

 response ~ age.refc.fo + dusz.cat.fo + ed.du.f + emp.ref.f +  

    geodist3.f + has.fone.f + healthdu.f + help.du.f + inc.ref.f +  

    maj.act.f + marryref.f + msa.stat.f + regionrf.f + r.e.ref.f +  

    sex.ref.f + type.psu.f + urb.stat.f 

 

> 

> m1.stepFwd$anova

Stepwise Model Path 

Analysis of Deviance Table

 

Initial Model:

response ~ age.refc.fo + dusz.cat.fo + ed.du.f + emp.ref.f + 

    geodist3.f + has.fone.f + healthdu.f + help.du.f + inc.ref.f + 

    maj.act.f + marryref.f + msa.stat.f + regionrf.f + r.e.ref.f + 

    sex.ref.f + type.psu.f + urb.stat.f

 

Final Model:

response ~ age.refc.fo + dusz.cat.fo + ed.du.f + emp.ref.f + 

    geodist3.f + has.fone.f + healthdu.f + help.du.f + inc.ref.f + 

    maj.act.f + marryref.f + msa.stat.f + regionrf.f + r.e.ref.f + 

    sex.ref.f + type.psu.f + urb.stat.f

 

 

  Step Df Deviance Resid. Df Resid. Dev      AIC

1      NA       NA      5311   4660.192 4752.192

>

 

 


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