绘制在简化版的SMO算法下生成的分类超平面,以及绘制在完整版的SMO算法下生成的分类超平面;python代码
时间: 2023-12-22 20:03:07 浏览: 63
下面是绘制在简化版SMO算法下生成的分类超平面的Python代码示例:
```python
import numpy as np
import matplotlib.pyplot as plt
# 定义简化版SMO算法生成的分类超平面函数
def plot_smo_simple():
# 生成数据集
X = np.array([[3, 3], [4, 3], [1, 1]])
y = np.array([1, 1, -1])
# 简化版SMO算法训练模型
alpha = np.zeros(len(X))
b = 0
m, n = X.shape
while True:
alpha_pairs_changed = 0
for i in range(m):
g_i = np.sum(alpha * y * np.dot(X, X[i])) + b
if y[i] * g_i < 1:
alpha[i] += 1
b += y[i]
alpha_pairs_changed += 1
if alpha_pairs_changed == 0:
break
# 绘制数据点
plt.scatter(X[:, 0], X[:, 1], c=y)
# 绘制分类超平面(即 w·x + b = 0)
w = np.sum(alpha * y * X.T, axis=1)
x0 = np.linspace(0, 5)
y0 = (-b - w[0] * x0) / w[1]
plt.plot(x0, y0)
plt.show()
# 调用简化版SMO算法生成分类超平面
plot_smo_simple()
```
下面是绘制在完整版SMO算法下生成的分类超平面的Python代码示例:
```python
import numpy as np
import matplotlib.pyplot as plt
# 定义完整版SMO算法生成的分类超平面函数
def plot_smo_full():
# 生成数据集
X = np.array([[3, 3], [4, 3], [1, 1]])
y = np.array([1, 1, -1])
# 定义核函数
def kernel(x_i, x_j):
return np.dot(x_i, x_j)
# 完整版SMO算法训练模型
C = 1.0
tol = 0.001
max_iter = 50
alpha = np.zeros(len(X))
b = 0
m, n = X.shape
K = np.zeros((m, m))
for i in range(m):
for j in range(m):
K[i, j] = kernel(X[i], X[j])
for iter in range(max_iter):
alpha_pairs_changed = 0
for i in range(m):
E_i = np.sum(alpha * y * K[i]) + b - y[i]
if (y[i] * E_i < -tol and alpha[i] < C) or (y[i] * E_i > tol and alpha[i] > 0):
j = np.random.choice(list(range(i)) + list(range(i+1, m)))
E_j = np.sum(alpha * y * K[j]) + b - y[j]
alpha_i_old, alpha_j_old = alpha[i], alpha[j]
if y[i] != y[j]:
L = max(0, alpha[j] - alpha[i])
H = min(C, C + alpha[j] - alpha[i])
else:
L = max(0, alpha[i] + alpha[j] - C)
H = min(C, alpha[i] + alpha[j])
if L == H:
continue
eta = 2 * K[i, j] - K[i, i] - K[j, j]
if eta >= 0:
continue
alpha[j] -= y[j] * (E_i - E_j) / eta
alpha[j] = np.clip(alpha[j], L, H)
if abs(alpha[j] - alpha_j_old) < tol:
alpha[j] = alpha_j_old
continue
alpha[i] += y[i] * y[j] * (alpha_j_old - alpha[j])
b1 = b - E_i - y[i] * (alpha[i] - alpha_i_old) * K[i, i] - y[j] * (alpha[j] - alpha_j_old) * K[i, j]
b2 = b - E_j - y[i] * (alpha[i] - alpha_i_old) * K[i, j] - y[j] * (alpha[j] - alpha_j_old) * K[j, j]
if 0 < alpha[i] < C:
b = b1
elif 0 < alpha[j] < C:
b = b2
else:
b = (b1 + b2) / 2
alpha_pairs_changed += 1
if alpha_pairs_changed == 0:
break
# 绘制数据点
plt.scatter(X[:, 0], X[:, 1], c=y)
# 绘制分类超平面(即 w·x + b = 0)
w = np.sum(alpha * y * X.T, axis=1)
x0 = np.linspace(0, 5)
y0 = (-b - w[0] * x0) / w[1]
plt.plot(x0, y0)
plt.show()
# 调用完整版SMO算法生成分类超平面
plot_smo_full()
```
注意:以上代码只是示例,实际使用时需要根据自己的数据集和问题进行修改。
阅读全文