WEKA J48 Classifier Example Using Jython

“”“
Jython-WEKA data mining example 
Author: Pradeep Kishore Gowda 
This Program demonstrates the use of Simple Classification
 Algorithm (Using j48 decision Tree) on Iris Data set 
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import java.io.FileReader as FR
import weka.core.Instances as Instances
import weka.classifiers.trees.J48 as J48
	

		
Load Data File
	
file = FR('iris.arff’)
data = Instances(file)
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The sample data reads like this 
relation iris
attribute sepallength numeric
attribute sepalwidth numeric
attribute petallength numeric
attribute petalwidth numeric
attribute class {Iris-setosa,Iris-versicolor,Iris-virginica}
@data
5.1,3.5,1.4,0.2,Iris-setosa
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#set the class Index – the index of the dependent variable
data.setClassIndex(4)
#create the model
j48 = J48
j48.buildClassifier(data)
#print out the built model
print j48
	

		
you do not have to call the j48.toString(),
		
My guess is Python’s default str method calls
	
#.toString Internally. ?
	

		
let us classify an instance and verify the result
	
myinstance = data.instance(0)
klass = j48.classifyInstance(myinstance) 
#0.0
#what does 0.0 mean?
print data.attribute(data.classIndex()).value(klass)
#'Iris-setosa’   

Update: This thread on wekalist gives a similar example.