title: Create a new weka Instance
body: <p>I'm new in Weka, I'm triying to create new instances to be labeled with a previous trained <code>MultilayerPerceptron</code>, I did't know very much about how to create an instance so I got the first instance from my training data and then modified it by changing the atributes values:</p>
  
  <pre><code>//Opening the model
  public boolean abrirModelo(String ruta) {
      try {
  
          clasificador = (MultilayerPerceptron) weka.core.SerializationHelper.read(ruta); 
  
          return true;
      } catch (IOException e) {
          System.out.println("Fallo la lectura del archivo");
          return false;
      } catch (ClassNotFoundException a) {
          System.out.println("Fallo el casting");
          return false;
      }catch(Exception e){
          System.out.println("Error con el castingo");
          return false;
      }
  }
  
  //getting the first instance to be modified
  public boolean inicializarInstancias(String directorio){
     archivo = new ArffLoader();
      try {
          archivo.setFile(new File(directorio));
          structure = archivo.getStructure();
          structure.setClassIndex(structure.numAttributes() - 1);
          actual = archivo.getNextInstance(structure); //instance to be used
      } catch (IOException ex) {
          System.out.println("Algo salio mal al cargar la estructura de lsa instancias");
      }
      return true;
  }
  
  //creating an instance from my local data using the previous instantiated actual instance, it is a List of Points with x and y
  public Instance convertir(LineaDeArchivo line) {
      int size = line.getDatos().size();
      for (int i = 0; i &lt; size; i+=2) {
          actual.setValue(i, line.getDatos().get(i).x);
          actual.setValue(i + 1, line.getDatos().get(i).y);
      }   
      return actual;
  }
  //getting the class 
  public String getClase(Instance e){
      try{
          double clase;
          clase = clasificador.classifyInstance(e);
          return structure.classAttribute().value((int) clase);
      }catch(Exception a){
          System.out.println("Algo salio mal con la clasificacion");
          return "?";
      }
  
  }
  </code></pre>
  
  <p>May be that is no the right way to do it, the clasifiers get the same class value to all the instances I give, I think the problem is the way I create the instance.    </p>
  
  <p>I hope someone could give me an advice, Thanks in advance</p>