direction finding algorithm

代码说明：

  利用信号本身的结构特征，通过附加不同的稀疏约束，该模型利用过完备字典进行信号分解，使其表示成字典中若干原子的线性组合，从而获得数据的精简表示。(By using the structural characteristics of the signal itself and adding different sparse constraints, the model decomposes the signal into linear combinations of atoms in the dictionary by using an over-complete dictionary, thus obtaining a simplified representation of the data.)