python实现简单神经网络算法

Glenna ·

更新时间:2024-11-15

· 744 次阅读

python实现简单神经网络算法，供大家参考，具体内容如下

python实现二层神经网络

包括输入层和输出层


import numpy as np 
#sigmoid function 
def nonlin(x, deriv = False): 
  if(deriv == True): 
    return x*(1-x) 
  return 1/(1+np.exp(-x)) 
#input dataset 
x = np.array([[0,0,1], 
       [0,1,1], 
       [1,0,1], 
       [1,1,1]]) 
#output dataset 
y = np.array([[0,0,1,1]]).T 
np.random.seed(1) 
#init weight value 
syn0 = 2*np.random.random((3,1))-1 
for iter in xrange(100000): 
  l0 = x             #the first layer,and the input layer  
  l1 = nonlin(np.dot(l0,syn0))  #the second layer,and the output layer 
  l1_error = y-l1 
  l1_delta = l1_error*nonlin(l1,True) 
  syn0 += np.dot(l0.T, l1_delta) 
print "outout after Training:" 
print l1


import numpy as np 
#sigmoid function 
def nonlin(x, deriv = False): 
  if(deriv == True): 
    return x*(1-x) 
  return 1/(1+np.exp(-x)) 
#input dataset 
x = np.array([[0,0,1], 
       [0,1,1], 
       [1,0,1], 
       [1,1,1]]) 
#output dataset 
y = np.array([[0,0,1,1]]).T 
np.random.seed(1) 
#init weight value 
syn0 = 2*np.random.random((3,1))-1 
for iter in xrange(100000): 
  l0 = x             #the first layer,and the input layer  
  l1 = nonlin(np.dot(l0,syn0))  #the second layer,and the output layer 
  l1_error = y-l1 
  l1_delta = l1_error*nonlin(l1,True) 
  syn0 += np.dot(l0.T, l1_delta) 
print "outout after Training:" 
print l1

这里，
l0:输入层

l1:输出层

syn0:初始权值

l1_error:误差

l1_delta:误差校正系数

func nonlin:sigmoid函数

可见迭代次数越多，预测结果越接近理想值，当时耗时也越长。

python实现三层神经网络

包括输入层、隐含层和输出层


import numpy as np 
def nonlin(x, deriv = False): 
  if(deriv == True): 
    return x*(1-x) 
  else: 
    return 1/(1+np.exp(-x)) 
#input dataset 
X = np.array([[0,0,1], 
       [0,1,1], 
       [1,0,1], 
       [1,1,1]]) 
#output dataset 
y = np.array([[0,1,1,0]]).T 
syn0 = 2*np.random.random((3,4)) - 1 #the first-hidden layer weight value 
syn1 = 2*np.random.random((4,1)) - 1 #the hidden-output layer weight value 
for j in range(60000): 
  l0 = X            #the first layer,and the input layer  
  l1 = nonlin(np.dot(l0,syn0)) #the second layer,and the hidden layer 
  l2 = nonlin(np.dot(l1,syn1)) #the third layer,and the output layer 
  l2_error = y-l2    #the hidden-output layer error 
  if(j%10000) == 0: 
    print "Error:"+str(np.mean(l2_error)) 
  l2_delta = l2_error*nonlin(l2,deriv = True) 
  l1_error = l2_delta.dot(syn1.T)   #the first-hidden layer error 
  l1_delta = l1_error*nonlin(l1,deriv = True) 
  syn1 += l1.T.dot(l2_delta) 
  syn0 += l0.T.dot(l1_delta) 
print "outout after Training:" 
print l2


import numpy as np 
def nonlin(x, deriv = False): 
  if(deriv == True): 
    return x*(1-x) 
  else: 
    return 1/(1+np.exp(-x)) 
#input dataset 
X = np.array([[0,0,1], 
       [0,1,1], 
       [1,0,1], 
       [1,1,1]]) 
#output dataset 
y = np.array([[0,1,1,0]]).T 
syn0 = 2*np.random.random((3,4)) - 1 #the first-hidden layer weight value 
syn1 = 2*np.random.random((4,1)) - 1 #the hidden-output layer weight value 
for j in range(60000): 
  l0 = X            #the first layer,and the input layer  
  l1 = nonlin(np.dot(l0,syn0)) #the second layer,and the hidden layer 
  l2 = nonlin(np.dot(l1,syn1)) #the third layer,and the output layer 
  l2_error = y-l2    #the hidden-output layer error 
  if(j%10000) == 0: 
    print "Error:"+str(np.mean(l2_error)) 
  l2_delta = l2_error*nonlin(l2,deriv = True) 
  l1_error = l2_delta.dot(syn1.T)   #the first-hidden layer error 
  l1_delta = l1_error*nonlin(l1,deriv = True) 
  syn1 += l1.T.dot(l2_delta) 
  syn0 += l0.T.dot(l1_delta) 
print "outout after Training:" 
print l2

您可能感兴趣的文章:Python实现的NN神经网络算法完整示例神经网络(BP)算法Python实现及应用Python实现的三层BP神经网络算法示例Python编程实现的简单神经网络算法示例python实现神经网络感知器算法人工神经网络算法知识点总结

神经网络算法神经网络算法 Python

1024 个赞