laplacian matrix

laplacian 矩阵

参考：

https://wenku.baidu.com/view/0b2bd2892e3f5727a5e962e6.html

http://blog.csdn.net/jinshengtao/article/details/18448355

https://www.zhihu.com/question/22098422

http://www.cnblogs.com/LeftNotEasy/archive/2011/01/19/svd-and-applications.html

http://blog.csdn.net/beiyangdashu/article/details/49300479