[R] [klaR package] [NaiveBayes] warning message numerical 0 probability

[Fabon Dzogang]

Thank you very much for this clarification,

Sincerely,
Fabon Dzogang.

2010/11/15 Uwe Ligges <ligges at statistik.tu-dortmund.de>:
>
>
> On 03.11.2010 16:26, Fabon Dzogang wrote:
>>
>> Hi,
>>
>> I run R 2.10.1 under ubuntu 10.04 LTS (Lucid Lynx) and klaR version 0.6-4.
>>
>> I compute a model over a 2 classes dataset (composed of 700 examples).
>> To that aim, I use the function NaiveBayes provided in the package
>> klaR.
>> When I then use the prediction function : predict(my_model, new_data).
>> I get the following warning :
>>
>> "In FUN(1:747[[747L]], ...) : Numerical 0 probability with observation
>> 458"
>>
>> As I did not find any documentation or any discussion concerning this
>> warning message, I looked in the klaR source code and found the
>> following line in predict.NaiveBayes.R :
>>
>> "warning("Numerical 0 probability with observation ", i)"
>
>
> Within Naive Bayes in order to calculate the posteriori probabilities of
> the classes it is necessary to calculate the probabilities of the
> observations given the classes. The function NaiveBayes prints a warning
> if all these probabilities are numerical 0, i.e. that the observation
> has a numerical probability of 0 for *all* classes. Usually this is only
> the case when the obs. is an extreme outlier.
>
> I will change the warning to say "all classes" in further releases of klaR.
>
> Best wishes,
> Uwe Ligges
>
>
>
>> Unfortunately, it is hard to get a clear picture of the whole process
>> reading the code. I wonder if someone could help me with the meaning
>> of this warning message.
>>
>> Sorry I did not provide an example, but I could not simulate the same
>> message over a small toy example.
>>
>> Thank you,
>>
>> Fabon Dzogang.
>>
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>



-- 
Fabon Dzogang