此问题已在此处有答案：

How to draw a line through a scatter graph with no overflow（2个答案）
4年前关闭。
我似乎无法弄清楚如何让线性回归线（又名最佳拟合线）跨越整个图表的宽度。它似乎只是在左边最远的数据点和右边最远的数据点上，而不是更远。我该如何解决这个问题？

import matplotlib.pyplot as plt
import numpy as np
from scipy import stats
from scipy.interpolate import *
import MySQLdb

# connect to MySQL database
def mysql_select_all():
    conn = MySQLdb.connect(host='localhost',
                           user='root',
                           passwd='XXXXX',
                           db='world')
    cursor = conn.cursor()
    sql = """
        SELECT
            GNP, Population
        FROM
            country
        WHERE
            Name LIKE 'United States'
                OR Name LIKE 'Canada'
                OR Name LIKE 'United Kingdom'
                OR Name LIKE 'Russia'
                OR Name LIKE 'Germany'
                OR Name LIKE 'Poland'
                OR Name LIKE 'Italy'
                OR Name LIKE 'China'
                OR Name LIKE 'India'
                OR Name LIKE 'Japan'
                OR Name LIKE 'Brazil';
    """

    cursor.execute(sql)
    result = cursor.fetchall()

    list_x = []
    list_y = []

    for row in result:
        list_x.append(('%r' % (row[0],)))

    for row in result:
        list_y.append(('%r' % (row[1],)))

    list_x = list(map(float, list_x))
    list_y = list(map(float, list_y))

    fig = plt.figure()
    ax1 = plt.subplot2grid((1,1), (0,0))

    p1 = np.polyfit(list_x, list_y, 1)          # this line refers to line of regression

    ax1.xaxis.labelpad = 50
    ax1.yaxis.labelpad = 50

    plt.plot(list_x, np.polyval(p1,list_x),'r-') # this refers to line of regression  
    plt.scatter(list_x, list_y, color = 'darkgreen', s = 100)
    plt.xlabel("GNP (US dollars)", fontsize=30)
    plt.ylabel("Population(in billions)", fontsize=30)
    plt.xticks([1000000, 2000000, 3000000, 4000000, 5000000, 6000000, 
                7000000, 8000000, 9000000],  rotation=45, fontsize=14)
    plt.yticks(fontsize=14)

    plt.show()
    cursor.close()

mysql_select_all()