@Override
    public List<Double> transform(List<Double> in) {
        List<Double> out = new ArrayList<Double>();
        for (int i = 0; i < in.size(); i++){
            if(in.get(i).equals(Matrix.UNKNOWN_VALUE)){
                out.add(columnCentroids.get(i));
            }
            else{
                out.add(new Double(in.get(i).doubleValue()));
            }
        }
        return out;
    }