Python Notes45:函数系数拟合

Demo

import numpy as np
import matplotlib.pyplot as plt

# 定义x、y散点坐标
x = [5000, 6000, 7050, 8410, 10000]
x = np.array(x)
print('x is :\n', x)
num = [0, 0.34, 0.625, 0.875, 1.13]

y = np.array(num)
print('y is :\n', y)
# 用4次多项式拟合
f1 = np.polyfit(x, y, 4)
print('f1 is :\n', f1)

p1 = np.poly1d(f1)
print('p1 is :\n', p1)

#也可使用yvals=np.polyval(f1, x)
yvals = p1(x)  # 拟合y值
print('yvals is :\n', yvals)
# 绘图
plot1 = plt.plot(x, y, 's', label='original values')
plot2 = plt.plot(x, yvals, 'r', label='polyfit values')

plt.ylim((1.5, 0))
plt.xlabel('x')
plt.ylabel('y')
plt.legend(loc=4)  # 指定legend的位置右下角
plt.title('polyfitting')
plt.show()