[R] GLM: Classification problem. Help!

[David Winsemius]

On Nov 18, 2009, at 5:12 PM, J_Laberga wrote:

>
> Hello,
> I need help with this. Let's say that I have n features that I want  
> to use
> to predict which class an observation belongs to. Using training  
> data I try
> to do the following:
>
>> training$result <- as.factor(training$result)
>> model <- glm(result ~., family=binomial("logit"), data = training)
>
> However, when I run the model on my test data I receive predictions  
> that
> have continuous values. I.e. if I have the classes 0 and 1 in  
> "results" I
> get predictions of 0.234235 and so on.
> How do I force the output to be just 0 or 1? What am I missing?

The fact that predict gives you probabilities? If you want a decision,  
then you need to specify a decision rule, i.e. a threshold.

>

David Winsemius, MD
Heritage Laboratories
West Hartford, CT