java - weka:将新实例添加到数据集

Question

我有一个 weka 数据集:

@attribute uid numeric
@attribute itemid numeric
@attribute rating numeric
@attribute timestamp numeric

@data
196 242 3   881250949
186 302 3   891717742
22  377 1   878887116
196 51  5   881250949
244 51  2   880606923

如果我想添加一个像这样的新实例:

244 59  2   880606923

我该怎么做？

类似这样的东西？

Instances newData = arffLoader.getDataSet();
    for (int i = 0; i < newData.numInstances(); i++) {
         Instance one = newData.instance(i);
         one.setDataset(data);
         data.add(one);
    }

Answer 1

尝试下面的代码。您需要做什么来为新值创建一个 double 组。使用 DenseInstance 类将它们添加到您的 Instances 对象中。

public static void main(String[] args) {


    String dataSetFileName = "stackoverflowQuestion.arff";
    Instances data = MyUtilsForWekaInstanceHelper.getInstanceFromFile(dataSetFileName);
    System.out.println("Before adding");
    System.out.println(data);


    double[] instanceValue1 = new double[data.numAttributes()];
    instanceValue1[0] = 244;
    instanceValue1[1] = 59;
    instanceValue1[2] = 2;
    instanceValue1[3] = 880606923;

    DenseInstance denseInstance1 = new DenseInstance(1.0, instanceValue1);

    data.add(denseInstance1);

    System.out.println("-----------------------------------------------------------");
    System.out.println("After adding");
    System.out.println(data);


public class MyUtilsForWekaInstanceHelper {

public static Instances getInstanceFromFile(String pFileName)
{
    Instances data = null;
    try {
        BufferedReader reader = new BufferedReader(new FileReader(pFileName));
        data = new Instances(reader);
        reader.close();
        // setting class attribute
        data.setClassIndex(data.numAttributes() - 1);
    }
    catch (Exception e) {
        throw new RuntimeException(e);
    } 
    return data;

}
  }

输出如下。

Before adding
@relation stackoverflowQuestion

@attribute uid numeric
@attribute itemid numeric
@attribute rating numeric
@attribute timestamp numeric

@data
196,242,3,881250949
186,302,3,891717742
22,377,1,878887116
196,51,5,881250949
244,51,2,880606923
---------------------------------------------------------------------------------
After adding
@relation stackoverflowQuestion

@attribute uid numeric
@attribute itemid numeric
@attribute rating numeric
@attribute timestamp numeric

@data
196,242,3,881250949
186,302,3,891717742
22,377,1,878887116
196,51,5,881250949
244,51,2,880606923
244,59,2,880606923