step1。我对一堆积分进行线性回归并得到一条直线。 step2。我通过平均这一点得到一个中心点 step3。我想在步骤1中找到一条垂直于回归线的线，并通过步骤2中提到的中心点。
我的想法：假设回归线y1 = k1 * x1 + b1，垂直线y2 = k2 * x2 + b2，则k2 = -1 / k1
问题：从图中看，两条直线看起来都不垂直。为什么？发生了什么
我的python代码：`
import numpy as np
import scipy.linalg
import matplotlib.pyplot as plt
from openpyxl import load_workbook
x = [140.0, 139.0, 145.0, 151.0, 156.0, 160.0, 162.0, 162.0, 156.0, 139.0, 129.0, 124.0, 125.0, 128.0, 127.0, 126.0, 126.0, 132.0, 139.0, 145.0, 150.0, 156.0, 155.0, 148.0, 135.0, 129.0, 125.0, 127.0, 128.0, 126.0, 123.0, 124.0, 130.0, 135.0, 142.0, 151.0, 158.0, 155.0, 148.0, 140.0, 126.0, 124.0, 127.0, 127.0, 126.0, 126.0, 126.0, 131.0, 138.0, 141.0, 159.0, 167.0, 162.0, 155.0, 147.0, 141.0, 138.0, 140.0, 140.0, 140.0, 138.0, 143.0, 150.0, 155.0, 163.0, 173.0, 178.0, 173.0]
y = [621.0, 621.0, 630.0, 638.0, 636.0, 635.0, 635.0, 634.0, 628.0, 623.0, 617.0, 614.0, 618.0, 622.0, 617.0, 610.0, 612.0, 622.0, 626.0, 623.0, 622.0, 624.0, 625.0, 618.0, 613.0, 607.0, 608.0, 614.0, 614.0, 608.0, 603.0, 612.0, 616.0, 617.0, 616.0, 618.0, 622.0, 622.0, 615.0, 609.0, 607.0, 610.0, 612.0, 607.0, 606.0, 601.0, 611.0, 617.0, 615.0, 614.0, 619.0, 624.0, 625.0, 619.0, 615.0, 613.0, 618.0, 622.0, 616.0, 610.0, 614.0, 628.0, 625.0, 624.0, 628.0, 638.0, 646.0, 645.0]
def get_center(x,y):
x = x[:-1]
y = y[:-1]
x0 = np.mean(x)
y0 = np.mean(y)
return x0, y0
#center point
x0,y0 = get_center(x,y)
#linear regression
# fit_fn is now a function which takes in x and returns an estimate for y
fit = np.polyfit(x,y,1)
fit_fn = np.poly1d(fit)
plt.plot(x0,y0,'bo')
#get the linear regression line
plt.plot(x,y, 'ro', x, fit_fn(x), '--k')
#get the perpendicular line going through the center point
plt.plot(x,(-1.0/fit[0])*(x-x0)+y0,'--b')
plt.grid(True)
plt.show()
this is the link of the graph I got by running the program
`
答案 0 :(得分：2)
因为x和y轴没有相同的比例
例如，添加第plt.axis([120, 180, 590, 650])行，让x轴和y轴显示相同数量的标签（60）
