在 Weka Java API 中创建字符串属性 [英] Creating a string attribute in Weka Java API

问题描述

我正在尝试使用 Weka 的 Java API 创建一个新的字符串属性...

I'm trying to create a new string Attribute using Weka's Java API...

通读API javadocs，看来这样做的方法是使用这个构造函数:

Reading through the API javadocs, it appears that the way to do so is to use this constructor:

Attribute

public Attribute(java.lang.String attributeName,
                 FastVector attributeValues)

    Constructor for nominal attributes and string attributes. If a null vector of attribute values is passed to the method, the attribute is assumed to be a string.

    Parameters:
        attributeName - the name for the attribute
        attributeValues - a vector of strings denoting the attribute values. Null if the attribute is a string attribute.

但我不知道应该传递给 attributeValues 参数的内容...

but I'm stuck as to what I should pass into the attributeValues parameter...

当我输入 null 时，Java 会抱怨受保护的对象
当我输入 Null 时，是语法错误
当我输入 new FastVector() 时，它变成了一个空的名义属性而不是一个字符串属性...
当我创建一个新对象时:

when I put in null, Java complains about protected objects
when I put in Null, it's syntax error
when I put in new FastVector(), it becomes a nominal attribute that is empty rather than a string attribute...
when I create a new object:

FastVector fv = new FastVector();
fv.addElement(null);

然后将 fv 传递给参数，它返回一个空指针异常...

and then pass fv into the argument, it returns a null pointer exception...

我到底应该在 attributeValues 参数中放入什么，以便它成为字符串属性?

what exactly should I put into the attributeValues argument so that it becomes a string attribute?

推荐答案

您必须将 null 强制转换为 FastVector.否则会有更多的方法应用于方法签名:

You have to cast the null to FastVector. Otherwise more methods would apply to the method signature:

    FastVector attributes = new FastVector();
    attributes.addElement(new Attribute("attr", (FastVector) null));

这里是动态创建实例的好资源:http://weka.wikispaces.com/Creating+an+ARFF+file

Here is a good resource for creating Instances on the fly: http://weka.wikispaces.com/Creating+an+ARFF+file

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