# -*- coding:utf-8 -*-
import numpy as np
import matplotlib.pyplot as plt
from scipy import optimize
#直线方程函数
def f_1(x, A, B):
  return A*x + B
#二次曲线方程
def f_2(x, A, B, C):
  return A*x*x + B*x + C
#三次曲线方程
def f_3(x, A, B, C, D):
  return A*x*x*x + B*x*x + C*x + D
def plot_test():
  plt.figure()
  #拟合点
  x0 = [1, 2, 3, 4, 5]
  y0 = [1, 3, 8, 18, 36]
  #绘制散点
  plt.scatter(x0[:], y0[:], 25, "red")
  #直线拟合与绘制
  A1, B1 = optimize.curve_fit(f_1, x0, y0)[0]
  x1 = np.arange(0, 6, 0.01)
  y1 = A1*x1 + B1
  plt.plot(x1, y1, "blue")
  #二次曲线拟合与绘制
  A2, B2, C2 = optimize.curve_fit(f_2, x0, y0)[0]
  x2 = np.arange(0, 6, 0.01)
  y2 = A2*x2*x2 + B2*x2 + C2
  plt.plot(x2, y2, "green")
  #三次曲线拟合与绘制
  A3, B3, C3, D3= optimize.curve_fit(f_3, x0, y0)[0]
  x3 = np.arange(0, 6, 0.01)
  y3 = A3*x3*x3*x3 + B3*x3*x3 + C3*x3 + D3
  plt.plot(x3, y3, "purple")
  plt.title("www.jb51.net test")
  plt.xlabel('x')
  plt.ylabel('y')
  plt.show()
  return
plot_test()

def f_gauss(x, A, B, C, sigma):
  return A*np.exp(-(x-B)**2/(2*sigma**2)) + C