How to implement linear regression in python

The steps to implement linear regression in Python language are: import the library to be used, read the data and perform preprocessing. Analyze data and establish a linear regression model, and conduct model training to test the model effect

It is very convenient to implement linear regression using the python language, because it provides multiple ready-made libraries, such as numpy.linalog .lstsq, pandas.ols and

scipy.stats.linregress, etc. In this article, we will use the linear_model.LinearRegression of the sklearn library, which supports any dimension and is very easy to use.

[Recommended tutorial: Python tutorial]

Two-dimensional straight line

Example: Linear equation y=a*x b; y=a*x b represents a straight line on the plane

In the following example, we will establish a linear regression model, by giving the house area to predict the price of a house

import pandas as pd
from io import StringIO
from sklearn import linear_model
import matplotlib.pyplot as plt
# 房屋面积与价格历史数据(csv文件)
csv_data = 'square_feet,price\n150,6450\n200,7450\n250,8450\n300,9450\n350,11450\n400,15450\n600,18450\n'
# 读入dataframe
df = pd.read_csv(StringIO(csv_data))
print(df)
# 建立线性回归模型
regr = linear_model.LinearRegression()
# 拟合
regr.fit(df['square_feet'].reshape(-1, 1), df['price']) # 注意此处.reshape(-1, 1)，因为X是一维的！
# 不难得到直线的斜率、截距
a, b = regr.coef_, regr.intercept_
# 给出待预测面积
area = 238.5
# 方式1：根据直线方程计算的价格
print(a * area + b)
# 方式2：根据predict方法预测的价格
print(regr.predict(area))
# 画图
# 1.真实的点
plt.scatter(df['square_feet'], df['price'], color='blue')
# 2.拟合的直线
plt.plot(df['square_feet'], regr.predict(df['square_feet'].reshape(-1,1)), color='red', linewidth=4)
plt.show()

Rendering:

##Three-dimensional plane

Linear equation z= a*x b*y c; z=a*x b*y c represents a plane in space

import numpy as np
from sklearn import linear_model
from mpl_toolkits.mplot3d import Axes3D
import matplotlib.pyplot as plt
xx, yy = np.meshgrid(np.linspace(0,10,10), np.linspace(0,100,10))
zz = 1.0 * xx + 3.5 * yy + np.random.randint(0,100,(10,10))

# 构建成特征、值的形式
X, Z = np.column_stack((xx.flatten(),yy.flatten())), zz.flatten()

# 建立线性回归模型
regr = linear_model.LinearRegression()
# 拟合
regr.fit(X, Z)
# 不难得到平面的系数、截距
a, b = regr.coef_, regr.intercept_
# 给出待预测的一个特征
x = np.array([[5.8, 78.3]])
# 方式1：根据线性方程计算待预测的特征x对应的值z（注意：np.sum）
print(np.sum(a * x) + b)
# 方式2：根据predict方法预测的值z
print(regr.predict(x))
# 画图
fig = plt.figure()
ax = fig.gca(projection='3d')
# 1.画出真实的点
ax.scatter(xx, yy, zz)
# 2.画出拟合的平面
ax.plot_wireframe(xx, yy, regr.predict(X).reshape(10,10))
ax.plot_surface(xx, yy, regr.predict(X).reshape(10,10), alpha=0.3)
plt.show()

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