更改Mallet中的目标字母表:字母表不匹配

Question

我很难从Mallet开发人员列表中获得帮助，所以我在这里尝试。

我有一个目标字母表为{A，B，C}的InstancesList，我需要将另一个分析的目标字母表更改为{A，NOT_A}。

到目前为止，我有以下代码(改编自其他Mallet源代码)，但我不断得到：

字母表不匹配:实例: 5976，null，InstanceList: 5976，2

...
InstanceList iListCopy = (InstanceList) instances.clone();

Alphabet blank = new Alphabet();
Alphabet newAlpha = new Alphabet();

//A and NOT_A cannot be found in alphabet, so add them.
newAlpha.lookupIndex("A", true);
newAlpha.lookupIndex("NOT_A", true);

Noop pipe = new Noop(blank, newAlpha);
InstanceList newIList = new InstanceList(pipe);

//iterate through each instance and change the target based on the
original value.
for (int i = 0; i < iListCopy.size(); i++) {
   Instance inst = iListCopy.get(i);

   FeatureVector original = (FeatureVector) inst.getData();
   Instance newInst = pipe.instanceFrom(new Instance(original,
newAlpha, inst.getName(), inst.getSource()));
   if (inst.getLabeling().toString().equals("A") {  
       newInst.setTarget("A");
   } else {
       newInst.setTarget("NOT_A");
   }
   newIList.add(newInst);   //FAILS with "Alphabets do not match."
}
...

有没有人对如何将目标字母表从{A，B，C}更改为{A，NOT_A}有什么建议？

Answer 1

目标应为标签。试试这个：

..
newInst.setTarget(((LabelAlphabet) newList.getTargetAlphabet()).lookupLabel("A"));
..
newInst.setTarget(((LabelAlphabet) newList.getTargetAlphabet()).lookupLabel("NOT_A"));