R help - Jan 2007 - logistic regression in R - changing defaults

Hello,

I was hoping for some advice in changing 2 defaults in a logistic regression.

1. It looks like the first category is the reference category?  In the 
following syntax 'where' has 4 levels, how can I make the reference 
category the third category?

model<- glm(cbind(sucesses, failures) ~ where + who + firstep + dxnarrow + 
age + sex + medyear, family = binomial, data=life.use)
model

2. Is it possible to round results to 4 decimal points? If so, what syntax 
is required?

Any assistance is appreciated,

Bob Green

an option is to use ?relevel(), e.g.,

life.use$where. <- relevel(life.use$where, 3)
model<- glm(cbind(sucesses, failures) ~ where. + who + firstep + 
dxnarrow +
            age + sex + medyear, family = binomial, data = life.use)
print(model, digits = 1)
print(model, digits = 2)
print(model, digits = 3)
print(model, digits = 4)


I hope it helps.

Best,
Dimitris

----
Dimitris Rizopoulos
Ph.D. Student
Biostatistical Centre
School of Public Health
Catholic University of Leuven

Address: Kapucijnenvoer 35, Leuven, Belgium
Tel: +32/(0)16/336899
Fax: +32/(0)16/337015
Web: http://med.kuleuven.be/biostat/
     http://www.student.kuleuven.be/~m0390867/dimitris.htm


----- Original Message ----- 
From: "Bob Green" <bgreen at dyson.brisnet.org.au>
To: <r-help at stat.math.ethz.ch>
Sent: Tuesday, January 09, 2007 1:16 PM
Subject: [R] logistic regression in R - changing defaults

> Hello,
>
> I was hoping for some advice in changing 2 defaults in a logistic 
> regression.
>
> 1. It looks like the first category is the reference category?  In 
> the
> following syntax 'where' has 4 levels, how can I make the reference
> category the third category?
>
> model<- glm(cbind(sucesses, failures) ~ where + who + firstep + 
> dxnarrow +
> age + sex + medyear, family = binomial, data=life.use)
> model
>
> 2. Is it possible to round results to 4 decimal points? If so, what 
> syntax
> is required?
>
> Any assistance is appreciated,
>
> Bob Green
>
> ______________________________________________
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> PLEASE do read the posting guide 
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
> 

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