神经网络预测python代码
时间: 2023-07-08 17:11:05 浏览: 43
以下是一个简单的神经网络预测Python代码示例:
```python
import numpy as np
from sklearn.neural_network import MLPRegressor
# 创建一个多层感知器模型
model = MLPRegressor(hidden_layer_sizes=(10, 5), activation='relu', solver='adam', max_iter=1000)
# 准备数据
X = np.array([[0, 0], [0, 1], [1, 0], [1, 1]])
y = np.array([0, 1, 1, 0])
# 训练模型
model.fit(X, y)
# 进行预测
prediction = model.predict([[0, 0], [0, 1], [1, 0], [1, 1]])
# 输出预测结果
print(prediction)
```
在这个示例中,我们使用了scikit-learn库中的多层感知器模型(MLPRegressor)。我们使用了一个包含两个隐藏层的神经网络,其中第一个隐藏层包含10个神经元,第二个隐藏层包含5个神经元。我们使用了ReLU作为激活函数,Adam作为优化算法,并且设置了最大迭代次数为1000。我们使用了一个简单的二元逻辑运算问题来演示如何进行预测。我们首先准备了输入数据和输出结果,然后使用fit()方法训练模型。最后,我们使用predict()方法对输入数据进行预测,并输出预测结果。
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pso优化的bp神经网络预测python代码
以下是使用PSO算法优化BP神经网络进行预测的Python代码示例:
```python
import numpy as np
class PSO_BP_Network:
def __init__(self, n_inputs, n_hidden, n_outputs):
# 初始化神经网络的结构
self.n_inputs = n_inputs
self.n_hidden = n_hidden
self.n_outputs = n_outputs
self.weights_ih = np.random.randn(self.n_hidden, self.n_inputs)
self.weights_ho = np.random.randn(self.n_outputs, self.n_hidden)
self.bias_h = np.random.randn(self.n_hidden, 1)
self.bias_o = np.random.randn(self.n_outputs, 1)
# 初始化PSO算法的参数
self.n_particles = 50
self.max_iter = 100
self.w = 0.5
self.c1 = 2
self.c2 = 2
self.velocity_ih = np.zeros_like(self.weights_ih)
self.velocity_ho = np.zeros_like(self.weights_ho)
self.best_position_ih = np.copy(self.weights_ih)
self.best_position_ho = np.copy(self.weights_ho)
self.best_error = float('inf')
def sigmoid(self, x):
# sigmoid函数
return 1 / (1 + np.exp(-x))
def feedforward(self, inputs):
# 前向传播
inputs = np.array(inputs).reshape(-1, 1)
hidden = self.sigmoid(np.dot(self.weights_ih, inputs) + self.bias_h)
outputs = self.sigmoid(np.dot(self.weights_ho, hidden) + self.bias_o)
return outputs
def train(self, training_inputs, training_outputs):
# 使用PSO和BP算法进行训练
for i in range(self.max_iter):
for j in range(self.n_particles):
# 更新粒子的速度和位置
r1 = np.random.rand(*self.weights_ih.shape)
r2 = np.random.rand(*self.weights_ih.shape)
self.velocity_ih = self.w * self.velocity_ih + \
self.c1 * r1 * (self.best_position_ih - self.weights_ih) + \
self.c2 * r2 * (self.weights_ih[j] - self.weights_ih)
r1 = np.random.rand(*self.weights_ho.shape)
r2 = np.random.rand(*self.weights_ho.shape)
self.velocity_ho = self.w * self.velocity_ho + \
self.c1 * r1 * (self.best_position_ho - self.weights_ho) + \
self.c2 * r2 * (self.weights_ho[j] - self.weights_ho)
self.weights_ih += self.velocity_ih
self.weights_ho += self.velocity_ho
# 使用当前的权重进行BP算法训练
error = 0
for k in range(len(training_inputs)):
inputs = training_inputs[k]
targets = training_outputs[k]
outputs = self.feedforward(inputs)
error += np.sum((targets - outputs) ** 2)
outputs_delta = (targets - outputs) * outputs * (1 - outputs)
hidden_delta = np.dot(self.weights_ho.T, outputs_delta) * hidden * (1 - hidden)
self.weights_ho += self.learning_rate * np.dot(outputs_delta, hidden.T)
self.weights_ih += self.learning_rate * np.dot(hidden_delta, inputs.T)
# 更新全局最优解
if error < self.best_error:
self.best_error = error
self.best_position_ih = np.copy(self.weights_ih)
self.best_position_ho = np.copy(self.weights_ho)
def predict(self, test_inputs):
# 使用训练好的神经网络进行预测
predicted_outputs = []
for inputs in test_inputs:
outputs = self.feedforward(inputs)
predicted_outputs.append(outputs)
return predicted_outputs
```
在上面的代码中,我们在PSO_BP_Network类中添加了一个predict方法,用于使用训练好的神经网络进行预测。在该方法中,我们遍历测试数据集,对每个输入进行前向传播,得到预测输出,并将其添加到predicted_outputs列表中。最后返回predicted_outputs作为预测结果。
bp神经网络预测python代码_纯Python搭建一个深度神经网络并用于房价预测
以下是纯Python搭建一个深度神经网络并用于房价预测的代码:
```python
import numpy as np
import pandas as pd
import matplotlib.pyplot as plt
# 读取数据
data = pd.read_csv('housing.csv')
x = data.iloc[:, 0:13]
y = data.iloc[:, 13]
# 归一化处理
x = (x - np.mean(x)) / np.std(x)
y = (y - np.mean(y)) / np.std(y)
# 划分数据集
train_size = int(len(x) * 0.8)
train_x = x.iloc[:train_size, :]
train_y = y[:train_size]
test_x = x.iloc[train_size:, :]
test_y = y[train_size:]
# 定义网络结构
input_size = 13
hidden_size = 5
output_size = 1
# 初始化权重和偏置
w1 = np.random.randn(input_size, hidden_size)
b1 = np.zeros((1, hidden_size))
w2 = np.random.randn(hidden_size, output_size)
b2 = np.zeros((1, output_size))
# 定义激活函数
def sigmoid(x):
return 1 / (1 + np.exp(-x))
# 定义损失函数
def mse_loss(y_true, y_pred):
return np.mean(np.square(y_true - y_pred))
# 定义前向传播函数
def forward(x):
z1 = np.dot(x, w1) + b1
a1 = sigmoid(z1)
z2 = np.dot(a1, w2) + b2
y_pred = z2
return y_pred, a1, z1
# 定义反向传播函数
def backward(y_pred, y_true, a1, z1, x):
delta2 = y_pred - y_true
dw2 = np.dot(a1.T, delta2)
db2 = np.sum(delta2, axis=0, keepdims=True)
delta1 = np.dot(delta2, w2.T) * a1 * (1 - a1)
dw1 = np.dot(x.T, delta1)
db1 = np.sum(delta1, axis=0)
return dw1, db1, dw2, db2
# 定义训练函数
def train(x, y, epochs, lr):
losses = []
for epoch in range(epochs):
y_pred, a1, z1 = forward(x)
loss = mse_loss(y, y_pred)
dw1, db1, dw2, db2 = backward(y_pred, y, a1, z1, x)
w1 -= lr * dw1
b1 -= lr * db1
w2 -= lr * dw2
b2 -= lr * db2
losses.append(loss)
if epoch % 1000 == 0:
print(f'Epoch {epoch}, Loss {loss}')
return losses
# 训练模型
losses = train(train_x, train_y, 10000, 0.01)
# 可视化损失函数
plt.plot(losses)
plt.xlabel('Epoch')
plt.ylabel('Loss')
plt.show()
# 预测测试集
test_pred, _, _ = forward(test_x)
test_pred = test_pred * np.std(y) + np.mean(y)
test_y = test_y * np.std(y) + np.mean(y)
# 计算测试集损失
test_loss = mse_loss(test_y, test_pred)
print(f'Test Loss: {test_loss}')
# 可视化预测结果
plt.plot(test_y, label='True')
plt.plot(test_pred, label='Predicted')
plt.legend()
plt.show()
```
需要注意的是,该代码中使用的是标准BP神经网络,如果要使用更高级的神经网络结构,可以使用TensorFlow、PyTorch等框架。