[R] Logistic Regression output baseline (reference) category

[David Winsemius]

> On Mar 15, 2016, at 1:27 PM, Michael Artz <michaeleartz at gmail.com> wrote:
> 
> Hi,
>   I am trying to use the summary from the glm function as a data source. I
> am using the call sink(<some file>) then
> summary(logisticRegModel)$coefficients then sink().

Since it's a matrix you may need to locate a function that write matrices to files. I seem to remember that the MASS package has one. 

>  The independent
> variables are categorical and thus there is always a baseline value for
> every category that is omitted from the glm output.

Well, it's not really omitted, so much as shared among all variables. For further reading in the halp pages consult:

?model.matrix
?contrasts
?contr.treatment

But you probably need to supplement that with an introductory text that covers R regression defaults.

>  I am interested in how
> to get the Z column for all of the categorical values.

The Z column? You meant the "z value" column. Again, since it's a matrix you need to use column indexing with "["

summary(logisticRegModel)$coefficients[  , "z value"]

Read up on the summary function for glm objects at:

?summary.glm


>  I don't see any row
> for the reference category.

What do you imagine the (Intercept) row to be doing? If you are having difficulty understanding this (which is not really an R-specific issue) there are probably already several explanations to similar questions on:

http://stats.stackexchange.com/

 
> 
> How can I get this Z value in the output?

Asked and answered.

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David Winsemius
Alameda, CA, USA