java - 在 weka 中添加一个新实例

Question

如何将新实例添加到我创建的现有实例对象？

这是一个例子:

ArrayList<Attribute> atts = new ArrayList<Attribute>(2);
ArrayList<String> classVal = new ArrayList<String>();
classVal.add("A");
classVal.add("B");
atts.add(new Attribute("content",(ArrayList<String>)null));
atts.add(new Attribute("@@class@@",classVal));

Instances dataRaw = new Instances("TestInstances",atts,0);

我想向 dataRaw 添加一个新实例。据我所知，我必须使用 dataRaw.add(Instance i) ....如果 Instance 类是一个接口(interface)，我如何创建一个实例对象？

提前致谢

Answer 1

让我们从一些亮点开始。

• weka 将每个实例值存储为 double[]。因此，您创建 double[] instanceValue1 并将值添加到此数组。
• 甚至字符串都存储在这个 double[] 中。您使用以下代码添加字符串值:

instanceValue1[0] = dataRaw.attribute(0).addStringValue("This is a string!");

• Instance 是接口(interface)，由两个类{SparseInstance , DenseInstance} 实现。我们使用以下代码将值数组添加到数据集:

dataRaw.add(new DenseInstance(1.0, instanceValue1));

完整的运行示例:

import java.util.ArrayList;

import weka.core.Attribute;
import weka.core.DenseInstance;
import weka.core.Instance;
import weka.core.Instances;

public class Program {
    public static void main(String[] args) {
        ArrayList<Attribute> atts = new ArrayList<Attribute>(2);
        ArrayList<String> classVal = new ArrayList<String>();
        classVal.add("A");
        classVal.add("B");
        atts.add(new Attribute("content",(ArrayList<String>)null));
        atts.add(new Attribute("@@class@@",classVal));

        Instances dataRaw = new Instances("TestInstances",atts,0);
        System.out.println("Before adding any instance");
        System.out.println("--------------------------");
        System.out.println(dataRaw);
        System.out.println("--------------------------");

        double[] instanceValue1 = new double[dataRaw.numAttributes()];

        instanceValue1[0] = dataRaw.attribute(0).addStringValue("This is a string!");
        instanceValue1[1] = 0;

        dataRaw.add(new DenseInstance(1.0, instanceValue1));

        System.out.println("After adding a instance");
        System.out.println("--------------------------");
        System.out.println(dataRaw);
        System.out.println("--------------------------");

        double[] instanceValue2 = new double[dataRaw.numAttributes()];

        instanceValue2[0] = dataRaw.attribute(0).addStringValue("This is second string!");
        instanceValue2[1] = 1;

        dataRaw.add(new DenseInstance(1.0, instanceValue2));

        System.out.println("After adding second instance");
        System.out.println("--------------------------");
        System.out.println(dataRaw);
        System.out.println("--------------------------");


    }

}

它的输出如下:

Before adding any instance
--------------------------
@relation TestInstances

@attribute content string
@attribute @@class@@ {A,B}

@data

--------------------------
After adding a instance
--------------------------
@relation TestInstances

@attribute content string
@attribute @@class@@ {A,B}

@data
'This is a string!',A
--------------------------
After adding second instance
--------------------------
@relation TestInstances

@attribute content string
@attribute @@class@@ {A,B}

@data
'This is a string!',A
'This is second string!',B
--------------------------