扣丁学堂Python培训简述Python实现的线性回归算法示例

2019-07-30 16:32:53 4554浏览

本篇文章扣丁学堂Python培训小编给小伙伴们实例分享一下Python实现的线性回归算法,涉及Python使用最小二乘法、梯度下降算法实现线性回归相关算法操作与使用技巧,需要的朋友就随小编一起来学习了解一下吧。

扣丁学堂Python培训简述Python实现的线性回归算法示例

代码:


#encoding:utf-8
"""
  Project: Using Python to Implement LineRegression Algorithm
"""
import numpy as np
import pandas as pd
from numpy.linalg import inv
from numpy import dot
from sklearn.model_selection import train_test_split
import matplotlib.pyplot as plt
from sklearn import linear_model
# 最小二乘法
def lms(x_train,y_train,x_test):
  theta_n = dot(dot(inv(dot(x_train.T, x_train)), x_train.T), y_train) # theta = (X'X)^(-1)X'Y
  #print(theta_n)
  y_pre = dot(x_test,theta_n)
  mse = np.average((y_test-y_pre)**2)
  #print(len(y_pre))
  #print(mse)
  return theta_n,y_pre,mse
#梯度下降算法
def train(x_train, y_train, num, alpha,m, n):
  beta = np.ones(n)
  for i in range(num):
    h = np.dot(x_train, beta)       # 计算预测值
    error = h - y_train.T         # 计算预测值与训练集的差值
    delt = 2*alpha * np.dot(error, x_train)/m # 计算参数的梯度变化值
    beta = beta - delt
    #print('error', error)
  return beta
if __name__ == "__main__":
  iris = pd.read_csv('iris.csv')
  iris['Bias'] = float(1)
  x = iris[['Sepal.Width', 'Petal.Length', 'Petal.Width', 'Bias']]
  y = iris['Sepal.Length']
  x_train, x_test, y_train, y_test = train_test_split(x, y, test_size=0.2, random_state=5)
  t = np.arange(len(x_test))
  m, n = np.shape(x_train)
  # Leastsquare
  theta_n, y_pre, mse = lms(x_train, y_train, x_test)
  # plt.plot(t, y_test, label='Test')
  # plt.plot(t, y_pre, label='Predict')
  # plt.show()
  # GradientDescent
  beta = train(x_train, y_train, 1000, 0.001, m, n)
  y_predict = np.dot(x_test, beta.T)
  # plt.plot(t, y_predict)
  # plt.plot(t, y_test)
  # plt.show()
  # sklearn
  regr = linear_model.LinearRegression()
  regr.fit(x_train, y_train)
  y_p = regr.predict(x_test)
  print(regr.coef_,theta_n,beta)
  l1,=plt.plot(t, y_predict)
  l2,=plt.plot(t, y_p)
  l3,=plt.plot(t, y_pre)
  l4,=plt.plot(t, y_test)
  plt.legend(handles=[l1, l2,l3,l4 ], labels=['GradientDescent', 'sklearn','Leastsquare','True'], loc='best')
  plt.show()

想要了解更多关于Python和人工智能方面内容的小伙伴,请关注扣丁学堂Python培训官网、微信等平台,扣丁学堂IT职业在线学习教育平台为您提供权威的Python开发环境搭建视频,Python培训后的前景无限,行业薪资和未来的发展会越来越好的,扣丁学堂老师精心推出的Python视频教程定能让你快速掌握Python从入门到精通开发实战技能。扣丁学堂Python技术交流群:279521237。


扣丁学堂微信公众号                          Python全栈开发爬虫人工智能机器学习数据分析免费公开课直播间


      【关注微信公众号获取更多学习资料】         【扫码进入Python全栈开发免费公开课】



查看更多关于"Python开发资讯"的相关文章>


标签: Python培训 Python视频教程 Python在线视频 Python学习视频 Python培训班
微信
微博
15311698296

全国免费咨询热线

邮箱:codingke@1000phone.com

官方群:148715490

北京千锋互联科技有限公司版权所有   北京市海淀区宝盛北里西区28号天丰利商场4层
京ICP备12003911号-6   Copyright © 2013 - 2019
返回顶部 返回顶部