LISTA代码Python实现
时间: 2023-11-05 16:59:04 浏览: 99
抱歉,作为AI语言模型,我无法直接编写代码。以下是一个简单的LISTA算法的Python实现示例,仅供参考:
```python
import numpy as np
def sparse_coding(Y, D, lambda_, max_iter, tol):
alpha = np.zeros((D.shape[1], Y.shape[1])) # initialize sparse codes
for i in range(max_iter):
# update sparse codes using soft thresholding
alpha = soft_thresholding(D.T @ Y + lambda_ * alpha, lambda_)
# check convergence
if np.linalg.norm(Y - D @ alpha) < tol:
break
return alpha
def soft_thresholding(x, lambda_):
return np.sign(x) * np.maximum(np.abs(x) - lambda_, 0)
def lista(Y, D, lambda_, max_iter, tol):
alpha = sparse_coding(Y, D, lambda_, max_iter, tol) # initial sparse codes
for i in range(max_iter):
# update dictionary using least squares
D = (Y @ alpha.T) @ np.linalg.inv(alpha @ alpha.T)
# update sparse codes
alpha = sparse_coding(Y, D, lambda_, max_iter, tol)
return D, alpha
```
其中,`sparse_coding`函数实现了LISTA算法中的稀疏编码过程,使用软阈值算子进行更新。`lista`函数则实现了LISTA算法的主要流程,通过交替更新字典和稀疏编码,最终得到稀疏表示和稀疏字典。
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