Thanks for your replies. It is quite useful for my situation. Following the answer, I re-built the whole SDG classifier and run it on my data set. However, I just found that the result is worst than the model I build with a set of Instances. 

And also I run the Weka 3.7 GUI on the same data set with the same settings. The results is much  better than  the model I build with a set of Instances. 

Could you tell me why it happens? please help me to solve this problem. 

Many thanks,


From: <> on behalf of Mark Hall <>
Sent: 09 November 2015 20:27
To: Weka machine learning workbench list.
Subject: Re: [Wekalist] Questions related to build an incremental Clasisfier
At a minimum, you need to know the structure of the training data in order to initialise an incremental classifier in Weka. In other words, the buildClassifier() method needs to be called once with an empty set of Instances (just attribute information defined). After this, you can call updateClassifier() with individual instances.


From: <> on behalf of Yanchao YU <>
Reply-To: "Weka machine learning workbench list." <>
Date: Monday, 9 November 2015 10:09 pm
To: "Weka machine learning workbench list." <>
Subject: [Wekalist] Questions related to build an incremental Clasisfier

Hi All, 

I am a beginner to use Weka on my project. I tried to implement an incremental Classifier (SGD) for learning unknown objects. I followed some tutorials for building classifier using existing data instances ( However, in my situation, I cannot receive the training samples in the beginning. Is it possible to build classifier without or with less instances? 

My code is shown below:

            _isExisted = true;

Thanks for your help in advance. 


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