# -*- coding: utf-8 -*-

 import numpy as np

 import matplotlib.pyplot as plt

 from certifi import __main__

 def cost(x,y,theta=np.zeros((2,1))):

    m=len(y);

    J=1.0/(2*m)*sum((x.dot(theta).flatten()-y)**2);

    return J;

 def gradientDesc(x,y,theat=np.zeros((2,1)),alpha=0.001,iterations=1500):

     m=len(y)

     J=[]

     for i in xrange(iterations):

         a=theat[0][0]-alpha*(1.0/m)*sum((x.dot(theat).flatten()-y)*x[:,0]);

         b=theat[1][0]-alpha*(1.0/m)*sum((x.dot(theat).flatten()-y)*1);

         theat[0][0],theat[1][0]=a,b

         print theat[0][0], theat[1][0]

         print cost(x, y, theat);

     return theat;

 if __name__=="__main__":

     x=np.array([[9,1],[15,1],[25,1],[14,1],[10,1],[18,1]]);

     y=np.array([39,56,93,61,50,75]);

     ans=gradientDesc(x, y);

     xx=[1,30]

     yy=[ans[0][0]*1+ans[1][0],ans[0][0]*30+ans[1][0]]

     plt.plot(xx,yy)

     plt.scatter(x[:,0],y)

     plt.show()

     print 'end'

 #显示数据

 '''

 plt.scatter(x,y);

 plt.show();

 '''