weka.core.UnassignedDataset在创建未标记的实例时发生异常 [英] weka.core.UnassignedDatasetException when creating an unlabeled instance

问题描述

我训练了一个IBK分类器，其中包含我手动创建的一些训练数据，如下所示：

I trained an IBK classifier with some training data that I created manually as following:

ArrayList<Attribute> atts = new ArrayList<Attribute>();
ArrayList<String> classVal = new ArrayList<String>();
classVal.add("C1");
classVal.add("C2");
atts.add(new Attribute("a"));
atts.add(new Attribute("b"));
atts.add(new Attribute("c"));
atts.add(new Attribute("d"));
atts.add(new Attribute("@@class@@", classVal));

Instances dataRaw = new Instances("TestInstances", atts, 0);
dataRaw.setClassIndex(dataRaw.numAttributes() - 1);
double[] instanceValue1 = new double[]{3,0,1,0,0};
dataRaw.add(new DenseInstance(1.0, instanceValue1));

double[] instanceValue2 = new double[]{2,1,1,0,0};
dataRaw.add(new DenseInstance(1.0, instanceValue2));

double[] instanceValue3 = new double[]{2,0,2,0,0};
dataRaw.add(new DenseInstance(1.0, instanceValue3));

double[] instanceValue4 = new double[]{1,3,0,0,1};
dataRaw.add(new DenseInstance(1.0, instanceValue4));

double[] instanceValue5 = new double[]{0,3,1,0,1};
dataRaw.add(new DenseInstance(1.0, instanceValue5));

double[] instanceValue6 = new double[]{0,2,1,1,1};
dataRaw.add(new DenseInstance(1.0, instanceValue6));

然后我建立了分类器：

IBk ibk = new IBk();
try {
    ibk.buildClassifier(dataRaw);

} catch (Exception e) {
    e.printStackTrace();
}

我想创建一个带有未标记类的新实例并对此实例进行分类，I尝试以下没有运气。

I want to create a new instance with unlabeled class and classify this instance, I tried the following with no luck.

IBk ibk = new IBk();
try {
    ibk.buildClassifier(dataRaw);
    double[] values = new double[]{3,1,0,0,-1};
    DenseInstance newInst = new DenseInstance(1.0,values);
    double classif = ibk.classifyInstance(newInst);
    System.out.println(classif);
} catch (Exception e) {
    e.printStackTrace();
}

我只是得到以下错误

weka.core.UnassignedDatasetException: DenseInstance doesn't have access to a dataset!
at weka.core.AbstractInstance.classAttribute(AbstractInstance.java:98)
at weka.classifiers.AbstractClassifier.classifyInstance(AbstractClassifier.java:74)
at TextCategorizationTest.instancesWithDoubleValues(TextCategorizationTest.java:136)
at TextCategorizationTest.main(TextCategorizationTest.java:33)

看起来像我我在创建新实例时做错了什么。如何准确创建一个未标记的实例？

Looks like I am doing something wrong while creating a new instance. How can I create an unlabeled instance exactly ?

提前致谢

推荐答案

问题在于这一行：

double classif = ibk.classifyInstance(newInst);

当您尝试对 newInst 进行分类时，Weka抛出异常，因为 newInst 没有与之关联的Instances对象（即数据集） - 因此它不知道它的类属性。

When you try to classify newInst, Weka throws an exception because newInst has no Instances object (i.e., dataset) associated with it - thus it does not know anything about its class attribute.

您应首先创建一个类似于dataRaw的新Instances对象，向其添加未标记的实例，设置类索引，然后尝试对其进行分类，例如：

You should first create a new Instances object similar to the dataRaw, add your unlabeled instance to it, set class index, and only then try classifying it, e.g.:

Instances dataUnlabeled = new Instances("TestInstances", atts, 0);
dataUnlabeled.add(newInst);
dataUnlabeled.setClassIndex(dataUnlabeled.numAttributes() - 1);        
double classif = ibk.classifyInstance(dataUnlabeled.firstInstance());

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