# User:Elgreengeeto/Python Linear Perceptron

- a dot product is the sum of the products of aligned-elements from two
- same-lengthed arrays

def dot_product(a, b):

sum = 0 i = 0 while i < len(a): sum += a[i] * b[i] i += 1 return sum

class Perceptron:

#percieve based on a list of inputs def percieve(self, inputs): #if there is not a list of weights, make one of = length to list of inputs if len(self.weights) < len(inputs): for ip in inputs: self.weights.append(self.defualt_weight) #get the dot product of those inputs with the bias and the input's weights with the bias's weight sum = dot_product(inputs + [self.bias], self.weights + [self.bias_weight]) return sum

#learn method compares output of percieve() to the expected output and adjusts weights by plus or minus #the learn rate which is incrementally decreased by a factor of 0.99 def learn(self, inputs, expected): if self.learn_rate < 0.001: return self.learn_rate = self.learn_rate * 0.999 print "learn rate is %s" % (self.learn_rate) train_step = (expected - self.percieve(inputs)) * self.learn_rate self.bias_weight += self.bias_weight * train_step print "bias weight is: %s" % (self.bias_weight) for i in xrange(len(inputs)): self.weights[i] += inputs[i] * train_step print "input %s weight is: %s" % (i, self.weights[i])

#this defines how a Perceptron object represents itself in the interpreter def __str__(self): return "Weights: %s. Threshhold: %s. Learn rate: %s." % (self.weights, self.threshhold, self.learn_rate) #same as above __repr__ = __str__

#defines initial values for a new Perceptron object def __init__(self): self.bias = 1.0 self.bias_weight = 0.0 self.defualt_weight = 0.0 self.weights = [] self.learn_rate = 1

- trains a perceptron according to data

def train(data, perceptron): for case in data: perceptron.learn(case[0],case[1])

- define a dataset to try and train a perceptron

data = [[[1.0],2.0],[[2.0],4.0],[[3.0],6.0]]

- do the damned thing

if __name__ == '__main__': subject = Perceptron() for i in range(100000): train(data, subject) print "final bias weight: %s, final input weights: %s" % (subject.bias_weight, subject.weights)