R help - Feb 2005 - problem with logistic regression

Hi,

we try to do a logistic regression with the function glm.
But we notice that this function don't give the same results as the SAS proc
catmod (differents estimate given).
We try to change the contrast on R system with:
>
options(contrasts=c(unordered="contr.SAS",ordered="contr.poly"))
We also try with brlr and logistf functions.
Unfortunately, the estimate aren't still the same.

Please could someone help us.

Thank you

--------------------------------------------------
This mail sent through Polytech'Lille WebMail (IMP)

CATMOD in SAS builds log-linear glms.  If you are truly trying to create
logistic
regressions in SAS, use PROC LOGISTIC instead.  If you really meant that you are
trying
to create log-linear models in R - then look up the usage of the function loglin
(e.g.
loglin())

Cheers,
Joe

Quoting Helene.Dryssens at eleves.polytech-lille.fr:
> Hi,
> 
> we try to do a logistic regression with the function glm.
> But we notice that this function don't give the same results as the SAS
proc
> catmod (differents estimate given).
> We try to change the contrast on R system with:
> >
options(contrasts=c(unordered="contr.SAS",ordered="contr.poly"))
> 
> We also try with brlr and logistf functions.
> Unfortunately, the estimate aren't still the same.
> 
> Please could someone help us.
> 
> Thank you
> 
> --------------------------------------------------
> This mail sent through Polytech'Lille WebMail (IMP)
> 
> ______________________________________________
> R-help at stat.math.ethz.ch mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html
> 

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Joseph J. Nocera
Ph.D. Candidate
NB Coop. Fish & Wildlife Research Unit
Biology Department - Univ. New Brunswick
Fredericton, NB
Canada   E3B 6E1
tel: (902) 679-5733

"Why does it have to be spiders?  Why can't it be 'follow the
butterflies'"?!
    - Ron Weasley, Harry Potter & The Chamber of Secrets

Helene.Dryssens at eleves.polytech-lille.fr writes:
> Hi,
> 
> we try to do a logistic regression with the function glm.
> But we notice that this function don't give the same results as the SAS
proc
> catmod (differents estimate given).
> We try to change the contrast on R system with:
> >
options(contrasts=c(unordered="contr.SAS",ordered="contr.poly"))
> 
> We also try with brlr and logistf functions.
> Unfortunately, the estimate aren't still the same.
contr.SAS is something of a contradiction in terms since SAS does not
use the same type of contrast in all procedures. I believe PROC CATMOD
is using sum contrasts (contr.sum), whereas contr.SAS gives you
something similar to PROC GENMOD (last level set to zero).

-- 
   O__  ---- Peter Dalgaard             Blegdamsvej 3  
  c/ /'_ --- Dept. of Biostatistics     2200 Cph. N   
 (*) \(*) -- University of Copenhagen   Denmark      Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard at biostat.ku.dk)             FAX: (+45) 35327907

Helene,

The problem is not with R, but with the specification of the
SAS procedure you used.  It would be simpler and more
comparable if you specify your model in SAS with Proc Logistic
or Proc Genmod.

See if they work out for you,

Tim

---- Original message ----
>Date: Mon,  7 Feb 2005 17:19:54 +0100
>From: Helene.Dryssens at eleves.polytech-lille.fr  
>Subject: [R] problem with logistic regression  
>To: r-help at stat.math.ethz.ch
>Cc: nathaliebouez at yahoo.fr
>
>Hi,
>
>we try to do a logistic regression with the function glm.
>But we notice that this function don't give the same results
as the SAS proc
>catmod (differents estimate given).
>We try to change the contrast on R system with:
>>
options(contrasts=c(unordered="contr.SAS",ordered="contr.poly"))
>
>We also try with brlr and logistf functions.
>Unfortunately, the estimate aren't still the same.
>
>Please could someone help us.
>
>Thank you
>
>--------------------------------------------------
>This mail sent through Polytech'Lille WebMail (IMP)
>
>______________________________________________
>R-help at stat.math.ethz.ch mailing list
>https://stat.ethz.ch/mailman/listinfo/r-help
>PLEASE do read the posting guide!
http://www.R-project.org/posting-guide.html