- https://blog.csdn.net/SPESEG/article/details/103857241
- https://stackoverflow.com/questions/17411940/matplotlib-scatter-plot-legend
- https://www.pythonheidong.com/blog/article/390742/1046d8297bcf330df550/ # 只画一个点
- https://www.freesion.com/article/6104727583/
- https://blog.csdn.net/wjh2622075127/article/details/87921674 # 分三次画
- https://www.cnblogs.com/aloiswei/p/8946809.html # 在簇处打上 label