Java Weka:如何指定拆分百分比？

Question

我编写了代码来创建模型并保存它.它工作正常.我的理解是,默认情况下,数据分为10倍.我想在创建模型时将数据分成两组(训练和测试).在Weka UI上,我可以使用"Percentage split"单选按钮来完成.我想知道如何通过代码来完成它.我希望它分为两部分,80%是培训,20%是测试.这是我的代码.

        FilteredClassifier model = new FilteredClassifier();
        model.setFilter(new StringToWordVector());
        model.setClassifier(new NaiveBayesMultinomial());
        try {
            model.buildClassifier(trainingSet);
        } catch (Exception e1) { // TODO Auto-generated catch block
            e1.printStackTrace();
        }

        ObjectOutputStream oos = new ObjectOutputStream(
                new FileOutputStream(
                        "/Users/me/models/MyModel.model"));
        oos.writeObject(model);
        oos.flush();
        oos.close();

trainingSet这里已经填充了Instances对象.有人可以帮我弄这个吗？

提前致谢!

Answer 1

在UI类ClassifierPanel的方法中startClassifier(),我找到了以下代码:

// Percent split

int trainSize = (int) Math.round(inst.numInstances() * percent
    / 100);
int testSize = inst.numInstances() - trainSize;
Instances train = new Instances(inst, 0, trainSize);
Instances test = new Instances(inst, trainSize, testSize);

所以随机化你的数据集......

trainingSet.randomize(new java.util.Random(0));

......我建议你trainingSet以同样的方式分裂你:

int trainSize = (int) Math.round(trainingSet.numInstances() * 0.8);
int testSize = trainingSet.numInstances() - trainSize;
Instances train = new Instances(trainingSet, 0, trainSize);
Instances test = new Instances(trainingSet, trainSize, testSize);

然后使用Classifier#buildClassifier(Instances data)80%的设置实例来训练分类器:

model.buildClassifier(train);

更新:感谢@ ChengkunWu的回答,我在上面添加了随机化步骤.

Answer 2

您可能还想将分组随机化.

data.randomize(new java.util.Random(0));