逻辑回归.py

# Logistic Regression

__author__ = '文刀'

# import lib
import numpy as np
import matplotlib.pyplot as plt

# def loaddata
def loaddata(filename):
    file = open(filename)
    x=[]
    y=[]
    for line in file.readlines():
        line = line.strip().split()
        x.append([1,float(line[0]),float(line[1])])
        y.append(float(line[-1]))
    xmat = np.mat(x)
    ymat = np.mat(y).T
    file.close()
    return xmat, ymat

# w calc
def w_calc(xmat, ymat,alpha=0.001,maxIter=10001):
    # W init
    W = np.mat(np.random.randn(3,1))
    w_save = []
    # W update
    for i in range(maxIter):
        H = 1/(1+np.exp(-xmat*W))
        dw = xmat.T*(H-ymat) # dw:(3,1)
        W -= alpha * dw
        if i % 100 ==0:
            w_save.append([W.copy(),i])
    return W, w_save


# implement
xmat, ymat= loaddata('lr_data.txt')
print('xmat:',xmat,xmat.shape)
print('ymat:',ymat,ymat.shape)
W,w_save = w_calc(xmat,ymat,0.001,10000) # w save
print('W:',W)

# show
for wi in w_save:
    plt.clf()
    w0 = wi[0][0,0]
    w1 = wi[0][1,0]
    w2 = wi[0][2,0]
    plotx1 = np.arange(2,6,0.01)
    plotx2 = -w0/w2-w1/w2*plotx1
    plt.plot(plotx1,plotx2,c='r',label='decision boundary')

    plt.scatter(xmat[:,1][ymat==0].A,xmat[:,2][ymat==0].A,marker='^',s=150,label='label=0')
    plt.scatter(xmat[:,1][ymat==1].A,xmat[:,2][ymat==1].A,s=150,label='label=1')
    plt.grid()
    plt.legend()
    plt.title('iter:%s'%np.str(wi[1]))
    plt.pause(0.001)
plt.show()