public void doLayout() {
    selections.clear();
    if (points == null) {
      points = new Vector<ExprPoint>();
    }
    points.clear();

    for (Pair<Integer, Double> p : watsonProbes) {
      ExprPoint ep = new ExprPoint(p.getFirst(), p.getLast(), '+');
      points.add(ep);
    }

    for (Pair<Integer, Double> p : crickProbes) {
      ExprPoint ep = new ExprPoint(p.getFirst(), p.getLast(), '-');
      points.add(ep);
    }
  }
 public void clearSelections() {
   selections.clear();
 }