2_3.py

import numpy as np
import matplotlib.pyplot as plt

def target_function(x):
    y=x**2
    return y

def derivative_function(x):
    return 2*x

def draw_function():
    x=np.linspace(-1.2,1.2)
    y=target_function(x)
    plt.plot(x,y)

def draw_gd(X):
    Y=[]
    for i in range(len(X)):
        Y.append(target_function(X[i]))
    plt.plot(X,Y)

if __name__=='__main__':
    x=1.2
    eta=0.3
    error=1e-3
    X=[]
    X.append(x)
    y=target_function(x)
    while y>error:
        x=x-eta*derivative_function(x)
        X.append(x)
        y=target_function(x)
        print("x=%f,y=%f"%(x,y))
    
    draw_function()
    draw_gd(X)
    plt.show()