错误在java代码中使用WEKA API时:类属性未设置?

我正在尝试在我的java代码中使用weka API。 我使用J48树分类来分类MySQL数据库中的数据集,但是我有这个错误:

Trying to add database driver (JDBC): RmiJdbc.RJDriver - Error, not in CLASSPATH? Trying to add database driver (JDBC): jdbc.idbDriver - Error, not in CLASSPATH? Trying to add database driver (JDBC): com.mckoi.JDBCDriver - Error, not in CLASSPATH? Trying to add database driver (JDBC): org.hsqldb.jdbcDriver - Error, not in CLASSPATH? weka.core.UnassignedClassException: weka.classifiers.trees.j48.C45PruneableClassifierTree: Class attribute not set! at weka.core.Capabilities.test(Capabilities.java:1086) at weka.core.Capabilities.test(Capabilities.java:1018) at weka.core.Capabilities.testWithFail(Capabilities.java:1297) ..... 

这是我的代码:

 try{ DatabaseLoader loader = new DatabaseLoader(); loader.setSource("jdbc:mysql://localhost:3306/cuaca","root","491754"); loader.setQuery("select * from data_training"); Instances data = loader.getDataSet(); jTextArea1.append(data.toString()); String[] options = new String[1]; options[0] = "U"; // unpruned tree J48 tree = new J48(); // new instance of tree tree.setOptions(options); // set the option tree.buildClassifier(data); // build classifier //Evaluation eval=new Evaluation(data); //eval.crossValidateModel(tree, data, 10, new Random(1)); //jTextArea1.append(eval.toSummaryString("\n HASILNYA \n", false)); }catch(IOException ioe){ioe.printStackTrace();} catch(Exception e){e.printStackTrace();} 

数据集实际出现在textarea中:

 @relation data_training @attribute Tmean numeric @attribute Tmax numeric @attribute Td numeric @attribute RH numeric @attribute SLP numeric @attribute STP numeric @attribute Wind_ave numeric @attribute Wind_max numeric @attribute Hujan {Y,T} @data 25.9,31.6,23.1,93.4,1008.5,998.2,2.6,12.9,Y 27.6,31.4,22.3,87,1009.6,999.3,0.8,3.1,T 27.4,32.6,21.9,86.1,1009.4,999.2,4.5,14.3,T 27.6,32.2,22.4,87.3,1009.1,998.9,2.4,8.2,T 

我想知道为什么会出现错误(Class Attribute Not Set !!)

您应该在将数据集传递给分类器之前为其设置类索引 。 您的分类器必须知道哪个是您的结果变量。
在这些线之后……

 loader.setQuery("select * from data_training"); Instances data = loader.getDataSet(); 

添加以下内容:

 data.setClassIndex(data.numAttributes() - 1); 

如果Hujan是你的类属性(结果变量)

有关详细信息,请参阅Api Docs

试试吧

 data.setClassIndex(1); 
  1. 你的类索引