} else { vals[i] = Instance.missingValue();
  protected Instance mergeInstances(Instance source, Instance dest) {    Instances outputFormat = outputFormatPeek();    double[] vals = new double[outputFormat.numAttributes()];    for(int i = 0; i < vals.length; i++) {      if (m_SelectedCols.isInRange(i)) {	if (source != null) {	  vals[i] = source.value(i);	}      } else {	vals[i] = dest.value(i);      }    }    Instance inst = null;    if (dest instanceof SparseInstance) {      inst = new SparseInstance(dest.weight(), vals);    } else {      inst = new Instance(dest.weight(), vals);    }    inst.setDataset(dest.dataset());    return inst;  }