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- #!/usr/bin/python
- class Perceptron(object):
- def __init__(self, input_num, activator):
- '''
- 初始化感知器,设置输入参数的个数,以及激活函数。
- 激活函数的类型为double -> double
- '''
- self.activator = activator
- # 权重向量初始化为0
- self.weights = [0.0 for _ in range(input_num)]
- # 偏置项初始化为0
- self.bias = 0.0
- def __str__(self):
- '''
- 打印学习到的权重、偏置项
- '''
- return 'weights\t:%s\nbias\t:%f\n' % (self.weights, self.bias)
- def predict(self, input_vec):
- '''
- 输入向量,输出感知器的计算结果
- '''
- # 把input_vec[x1,x2,x3...]和weights[w1,w2,w3,...]打包在一起
- # 变成[(x1,w1),(x2,w2),(x3,w3),...]
- # 然后利用map函数计算[x1*w1, x2*w2, x3*w3]
- # 最后利用reduce求和
- return self.activator(
- reduce(lambda a, b: a + b,
- map(lambda (x, w): x * w,
- zip(input_vec, self.weights))
- , 0.0) + self.bias)
- def train(self, input_vecs, labels, iteration, rate):
- '''
- 输入训练数据:一组向量、与每个向量对应的label;以及训练轮数、学习率
- '''
- for i in range(iteration):
- self._one_iteration(input_vecs, labels, rate)
- def _one_iteration(self, input_vecs, labels, rate):
- '''
- 一次迭代,把所有的训练数据过一遍
- '''
- # 把输入和输出打包在一起,成为样本的列表[(input_vec, label), ...]
- # 而每个训练样本是(input_vec, label)
- samples = zip(input_vecs, labels)
- # 对每个样本,按照感知器规则更新权重
- for (input_vec, label) in samples:
- # 计算感知器在当前权重下的输出
- output = self.predict(input_vec)
- # 更新权重
- self._update_weights(input_vec, output, label, rate)
- def _update_weights(self, input_vec, output, label, rate):
- '''
- 按照感知器规则更新权重
- '''
- # 把input_vec[x1,x2,x3,...]和weights[w1,w2,w3,...]打包在一起
- # 变成[(x1,w1),(x2,w2),(x3,w3),...]
- # 然后利用感知器规则更新权重
- delta = label - output
- self.weights = map(
- lambda (x, w): w + rate * delta * x,
- zip(input_vec, self.weights))
- # 更新bias
- self.bias += rate * delta
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