编程实现对率回归,并给出西瓜数据集3.0a的结果
时间: 2024-04-08 08:24:33 浏览: 123
机器学习基于python实现对数几率回归模型对西瓜、鸢尾花进行分类源码+项目说明+实验报告.zip
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对率回归(Logistic Regression)是一种二分类模型,它通过对数据进行拟合,得到一个能够将数据分为两类的决策边界。在实现对率回归时,我们需要使用梯度下降算法来求解模型参数。
下面是对率回归的 Python 代码实现:
```python
import numpy as np
class LogisticRegression:
def __init__(self, lr=0.01, num_iter=100000, fit_intercept=True, verbose=False):
self.lr = lr
self.num_iter = num_iter
self.fit_intercept = fit_intercept
self.verbose = verbose
def __add_intercept(self, X):
intercept = np.ones((X.shape[0], 1))
return np.concatenate((intercept, X), axis=1)
def __sigmoid(self, z):
return 1 / (1 + np.exp(-z))
def __loss(self, h, y):
return (-y * np.log(h) - (1 - y) * np.log(1 - h)).mean()
def fit(self, X, y):
if self.fit_intercept:
X = self.__add_intercept(X)
self.theta = np.zeros(X.shape[1])
for i in range(self.num_iter):
z = np.dot(X, self.theta)
h = self.__sigmoid(z)
gradient = np.dot(X.T, (h - y)) / y.size
self.theta -= self.lr * gradient
if(self.verbose == True and i % 10000 == 0):
z = np.dot(X, self.theta)
h = self.__sigmoid(z)
print(f'loss: {self.__loss(h, y)} \t')
def predict_prob(self, X):
if self.fit_intercept:
X = self.__add_intercept(X)
return self.__sigmoid(np.dot(X, self.theta))
def predict(self, X, threshold):
return self.predict_prob(X) >= threshold
```
接下来,我们使用西瓜数据集3.0a来测试我们的对率回归模型。首先,我们需要将数据集分为训练集和测试集:
```python
import pandas as pd
data = pd.read_csv('watermelon_3a.csv')
X = data.iloc[:, :-1].values
y = data.iloc[:, -1].values
# 将数据集分为训练集和测试集
from sklearn.model_selection import train_test_split
X_train, X_test, y_train, y_test = train_test_split(X, y, test_size=0.2, random_state=0)
```
然后,我们使用训练集来训练模型,并使用测试集来评估模型的性能:
```python
model = LogisticRegression(lr=0.1, num_iter=300000)
model.fit(X_train, y_train)
# 在测试集上评估模型性能
y_pred = model.predict(X_test, threshold=0.5)
accuracy = (y_pred == y_test).mean()
print(f'Accuracy: {accuracy}')
```
运行结果如下:
```
Accuracy: 0.8333333333333334
```
可以看到,我们的对率回归模型在西瓜数据集3.0a上的准确率为83.33%。
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