bp神经网络python糖尿病
时间: 2023-06-12 22:03:15 浏览: 46
以下是一个实现用于预测糖尿病的BP神经网络的Python代码示例:
首先,我们需要导入一些必要的库和模块:
```python
import numpy as np
import pandas as pd
from sklearn.model_selection import train_test_split
from sklearn.preprocessing import StandardScaler
from sklearn.metrics import accuracy_score
```
接下来,我们将读取一个包含糖尿病患者数据的CSV文件,并将其拆分为训练集和测试集:
```python
# 读取数据
data = pd.read_csv('diabetes.csv')
# 将数据拆分为自变量和因变量
X = data.iloc[:, :-1].values
y = data.iloc[:, -1].values
# 将数据拆分为训练集和测试集
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2)
```
接下来,我们将对数据进行标准化处理:
```python
# 对自变量进行标准化处理
scaler = StandardScaler()
X_train = scaler.fit_transform(X_train)
X_test = scaler.transform(X_test)
```
然后,我们将定义一个包含一个隐藏层和一个输出层的BP神经网络:
```python
class NeuralNetwork:
def __init__(self):
# 初始化权重和偏差
self.weights1 = np.random.randn(8, 4)
self.bias1 = np.random.randn(1, 4)
self.weights2 = np.random.randn(4, 1)
self.bias2 = np.random.randn(1, 1)
def sigmoid(self, z):
# sigmoid函数
return 1 / (1 + np.exp(-z))
def sigmoid_derivative(self, z):
# sigmoid函数的导数
return self.sigmoid(z) * (1 - self.sigmoid(z))
def forward(self, X):
# 前向传播
self.z1 = np.dot(X, self.weights1) + self.bias1
self.a1 = self.sigmoid(self.z1)
self.z2 = np.dot(self.a1, self.weights2) + self.bias2
self.a2 = self.sigmoid(self.z2)
return self.a2
def backward(self, X, y, y_pred):
# 反向传播
d2 = (y_pred - y) * self.sigmoid_derivative(self.z2)
d1 = np.dot(d2, self.weights2.T) * self.sigmoid_derivative(self.z1)
self.weights2 -= 0.1 * np.dot(self.a1.T, d2)
self.bias2 -= 0.1 * np.sum(d2, axis=0, keepdims=True)
self.weights1 -= 0.1 * np.dot(X.T, d1)
self.bias1 -= 0.1 * np.sum(d1, axis=0)
def train(self, X, y):
# 训练模型
y_pred = self.forward(X)
self.backward(X, y, y_pred)
def predict(self, X):
# 预测结果
y_pred = self.forward(X)
y_pred[y_pred > 0.5] = 1
y_pred[y_pred <= 0.5] = 0
return y_pred
```
最后,我们将使用训练集对模型进行训练,并使用测试集对其进行评估:
```python
# 初始化神经网络
nn = NeuralNetwork()
# 训练模型
for i in range(1000):
nn.train(X_train, y_train)
# 预测结果
y_pred = nn.predict(X_test)
# 计算准确率
accuracy = accuracy_score(y_test, y_pred)
print('Accuracy:', accuracy)
```
这是一个简单的用于预测糖尿病的BP神经网络的Python示例。请注意,此代码仅用于演示目的。在实际应用中,您需要使用更多的技巧和技术来提高模型的准确性和性能。