DGM21作为灰色预测里对于S形摆动序列具有较好的预测效果，较GM（1,1）而言，预测的准确性大大提高，文件里有源码和预测效果图。(As a grey prediction, DGM21 has better prediction effect on S shape swing sequence. Compared with GM (1,1), the prediction accuracy is improved greatly. There are source code and predi