Using LibSVMLearner

Lewisham

Hi again!
I'm trying to use LibSVMLearner with a one-class setup, as I've heard this is a great way to do anomaly detection. However, whenever I use it (such as in the XML below), I get a null pointer exception.

All I'm doing is turning on the learner to be one-class. Doing this causes it to throw the null exception. If I leave it as C-SVC, it works. I presume there's some magic numbers I'm not giving it when I turn on one-class, but I don't know what it is. I'm feeding it a nominal true/false label, with the attributes being all numeric.

The exception is:

java.lang.NullPointerException
    at com.rapidminer.operator.learner.functions.kernel.LibSVMModel.performPrediction(LibSVMModel.java:139)
    at com.rapidminer.operator.learner.PredictionModel.apply(PredictionModel.java:77)
    at com.rapidminer.operator.ModelApplier.apply(ModelApplier.java:84)
    at com.rapidminer.operator.Operator.apply(Operator.java:666)
    at com.rapidminer.operator.OperatorChain.apply(OperatorChain.java:416)
    at com.rapidminer.operator.Operator.apply(Operator.java:666)
    at com.rapidminer.Process.run(Process.java:695)
    at com.rapidminer.Process.run(Process.java:665)
    at com.rapidminer.Process.run(Process.java:655)
    at com.rapidminer.gui.ProcessThread.run(ProcessThread.java:61)

and the XML is:

<operator name="Root" class="Process" breakpoints="after" expanded="yes">
    <parameter key="logverbosity"	value="status"/>
    <parameter key="logfile"	value="/Users/cflewis/Documents/Computing/0809/Spring/Data mining/Final/output.log"/>
    <operator name="Load Training Set" class="CSVExampleSource">
        <parameter key="filename"	value="/Users/cflewis/Documents/Computing/0809/Spring/Data mining/Final/data.csv"/>
    </operator>
    <operator name="AttributeSubsetPreprocessing" class="AttributeSubsetPreprocessing" expanded="yes">
        <parameter key="condition_class"	value="attribute_name_filter"/>
        <parameter key="attribute_name_regex"	value="label"/>
        <operator name="Numerical2Binominal" class="Numerical2Binominal">
        </operator>
    </operator>
    <operator name="ChangeAttributeRole" class="ChangeAttributeRole">
        <parameter key="name"	value="label"/>
        <parameter key="target_role"	value="label"/>
    </operator>
    <operator name="AttributeFilter" class="AttributeFilter">
        <parameter key="condition_class"	value="is_numerical"/>
    </operator>
    <operator name="AbsoluteStratifiedSampling" class="AbsoluteStratifiedSampling">
        <parameter key="sample_size"	value="1000"/>
    </operator>
    <operator name="LibSVMLearner" class="LibSVMLearner">
        <parameter key="svm_type"	value="one-class"/>
        <list key="class_weights">
        </list>
    </operator>
    <operator name="CSVExampleSource" class="CSVExampleSource">
        <parameter key="filename"	value="/Users/cflewis/Documents/Computing/0809/Spring/Data mining/Final/DataminingContest2009.Task1.Test.Inputs"/>
    </operator>
    <operator name="AttributeFilter (2)" class="AttributeFilter">
        <parameter key="condition_class"	value="is_numerical"/>
    </operator>
    <operator name="ModelApplier" class="ModelApplier">
        <list key="application_parameters">
        </list>
    </operator>
    <operator name="ExcelExampleSetWriter" class="ExcelExampleSetWriter">
        <parameter key="excel_file"	value="/Users/cflewis/Documents/Computing/0809/Spring/Data mining/Final/decisiontree_results.xls"/>
    </operator>
</operator>

The XML may look slightly odd as it's loading a training set, training on it, saving the model, then reloading it to be used with a test set. It is applying it to the test set that is failing.

I've no idea what I'm doing wrong!  Any help is appreciated!

land

Hi,
unfortunately your aren't doing anything wrong. Instead that's a bug occuring if you chose oneClass SVM, because the output of the model awaits support vectors which aren't given by one class SVM. That's why it crashes.
The good new is: You can use the model if you don't take a look at it. You can generate and save it, or apply it, as long as it is not shown in the result tabs.
The better news: The bug is resolved in the upcoming version

Greetings,
  Sebastian

Lewisham

land wrote:

Hi, unfortunately your aren't doing anything wrong. Instead that's a bug occuring if you chose oneClass SVM, because the output of the model awaits support vectors which aren't given by one class SVM. That's why it crashes. The good new is: You can use the model if you don't take a look at it. You can generate and save it, or apply it, as long as it is not shown in the result tabs. The better news: The bug is resolved in the upcoming version Greetings,   Sebastian

How does one stop it showing in the results tabs? I don't have a breakpoint or anything, but the error is occurring during the model application, so it never reaches the point where it writes out a spreadsheet of the results to disk.

land

Hi,
good news: The bug occurs only if the one class svm is used in the wrong way. As the name indicates, the svm only works with examples of ONE class. So make sure, the label attribute only contains one value, and the mapping of the label, too.
Here is a example process setup, where the examples of one class are filtered and then the mapping is corrected. The SVM then works.

<operator name="Root" class="Process" expanded="yes">
    <operator name="ExampleSetGenerator" class="ExampleSetGenerator">
        <parameter key="target_function"	value="sum classification"/>
    </operator>
    <operator name="ExampleFilter" class="ExampleFilter">
        <parameter key="condition_class"	value="attribute_value_filter"/>
        <parameter key="parameter_string"	value="label = positive"/>
    </operator>
    <operator name="Mapping" class="Mapping" breakpoints="after">
        <parameter key="attributes"	value="label"/>
        <parameter key="apply_to_special_features"	value="true"/>
        <list key="value_mappings">
        </list>
    </operator>
    <operator name="LibSVMLearner" class="LibSVMLearner">
        <parameter key="svm_type"	value="one-class"/>
        <list key="class_weights">
        </list>
    </operator>
    <operator name="ExampleSetGenerator (2)" class="ExampleSetGenerator">
        <parameter key="target_function"	value="sum classification"/>
    </operator>
    <operator name="ModelApplier" class="ModelApplier">
        <list key="application_parameters">
        </list>
    </operator>
</operator>

Greetings,
  Sebastian

PS: In further versions, a more helpfull error message will be displayed