R help - Sep 2013 - summary(object) not showing all values of a factor

Dear all,

I am encountering some odd results from the summary(object) command for
coxph and hurdle models. In both cases the result of summary(object)
function leaves out one of the categories of a categorical variable used in
the model. It is typically the first category if sorted alphabetically. Is
there any way around this problem?

For example, if I have categorical variable "type" with values
{A,B,C,D,E},
it typically leaves out A in the result of the summary.

Thanks!

	[[alternative HTML version deleted]]

These are **not** odd results. You just don't understand how linear models
work, in particular, you need to understand contrasts for categorical
factors.

As this is not the place for a statistics tutorial, I suggest you read up
on linear models or consult a local expert.

Cheers,
Bert


On Tue, Sep 3, 2013 at 11:51 AM, Soumitro Dey
<soumitrodey1@gmail.com>wrote:
> Dear all,
>
> I am encountering some odd results from the summary(object) command for
> coxph and hurdle models. In both cases the result of summary(object)
> function leaves out one of the categories of a categorical variable used in
> the model. It is typically the first category if sorted alphabetically. Is
> there any way around this problem?
>
> For example, if I have categorical variable "type" with values
{A,B,C,D,E},
> it typically leaves out A in the result of the summary.
>
> Thanks!
>
>         [[alternative HTML version deleted]]
>
> ______________________________________________
> R-help@r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide
> http://www.R-project.org/posting-guide.html
> and provide commented, minimal, self-contained, reproducible code.
>


-- 

Bert Gunter
Genentech Nonclinical Biostatistics

Internal Contact Info:
Phone: 467-7374
Website:
http://pharmadevelopment.roche.com/index/pdb/pdb-functional-groups/pdb-biostatistics/pdb-ncb-home.htm

	[[alternative HTML version deleted]]

Hi

see

?contrasts
?model.matrix

go through archives

and through chapter

11.1.1 Contrasts

from R-Intro document.

Anyway, when you go through this chapter you will probably benefit from reading
previous chapters too.

Regards
Petr

> -----Original Message-----
> From: r-help-bounces at r-project.org [mailto:r-help-bounces at r-
> project.org] On Behalf Of Soumitro Dey
> Sent: Tuesday, September 03, 2013 8:51 PM
> To: r-help at r-project.org
> Subject: [R] summary(object) not showing all values of a factor
> 
> Dear all,
> 
> I am encountering some odd results from the summary(object) command for
> coxph and hurdle models. In both cases the result of summary(object)
> function leaves out one of the categories of a categorical variable
> used in the model. It is typically the first category if sorted
> alphabetically. Is there any way around this problem?
> 
> For example, if I have categorical variable "type" with values
> {A,B,C,D,E}, it typically leaves out A in the result of the summary.
> 
> Thanks!
> 
> 	[[alternative HTML version deleted]]
> 
> ______________________________________________
> R-help at r-project.org mailing list
> https://stat.ethz.ch/mailman/listinfo/r-help
> PLEASE do read the posting guide http://www.R-project.org/posting-
> guide.html
> and provide commented, minimal, self-contained, reproducible code.