logisticregression

  1 from numpy import *
  2 import random
  3 import time
  4 st = time.time()
  5
  6 def loaddata(filename):
  7     fr = open(‘‘.join([filename, ‘.txt‘])).readlines()
  8     trainx = [[1] + map(float, line.split()[:-1]) for line in fr] # trainx = [[1,12.2,22.4],[1,22.3,31.2],...]
  9     trainy = [[float(line.split()[-1])] for line in fr] # trainy = [0,1,1,0,...]
 10     return trainx, trainy
 11
 12 def sigmod(z):
 13     return 1.0 / (1 + exp(-z))
 14
 15 def optimizaion(trainx, trainy):
 16     trainxmat = mat(trainx)
 17     m = len(trainx)
 18     # beta = [0,0,0]
 19     beta = ones((len(trainx[0]),1)) # array
 20     # maxiter
 21     M = 500
 22     """
 23     # error permid
 24     e =
 25     """
 26     """
 27     for i in xrange(M):
 28         #if error2sum > e:
 29         # z = betat.T * x = trainx (matricdoc)* beta = [beta.Tx1,beta.Tx2,...,beta.Txn]
 30         sigmodz = sigmod(trainxmat * beta)
 31         # [error_i = yi - sigmod(zi)]
 32         error = trainy - sigmodz
 33         # update beta
 34         beta += alpha * trainxmat.T * error
 35         print beta
 36         """
 37     # random gradascent
 38     for j in xrange(M):
 39         for i in xrange(m):
 40             # per span
 41             alpha = 0.01 + 4 / (1.0 + i +j)
 42             randid = random.randint(0, m - 1)
 43             sigmodz = sigmod(trainxmat[randid] * beta)
 44             error = trainy[randid] - sigmodz
 45             beta += alpha * trainxmat[randid].T * error
 46             #print beta
 47
 48     return beta
 49
 50
 51 def logregress(testx, beta):
 52     if mat(testx) * beta > 0: return [1.0]
 53     else: return [0.0]
 54
 55 def main():
 56     # step 1: loading data...
 57     print "step 1: loading data..."
 58     trainx, trainy = loaddata(‘horseColicTraining‘)
 59     testx, testy = loaddata(‘horseColicTest‘)
 60     """
 61     print ‘trainx‘, trainx
 62     print ‘trainy‘, trainy
 63     print ‘testx‘, testx
 64     print ‘testy‘, testy
 65     print ‘testy[2]‘,testy[2]
 66     """
 67
 68     # step 2: training...
 69     print "step 2: training..."
 70     beta = optimizaion(trainx, trainy)
 71     #print "beta = ",beta
 72
 73     # step 3: testing...
 74     print "step 3: testing..."
 75     numTests = 10; errorSum = 0.0; l = len(testx)
 76     for j in xrange(numTests):
 77         errorcount = 0.0
 78         #print ‘the total number is: ‘,l
 79         for i in xrange(l):
 80             if logregress(testx[i], beta) != testy[i]:
 81                 errorcount += 1
 82         #print "the number of error is: ", errorcount
 83         print "the error rate is: ", (errorcount / l)
 84         errorSum += (errorcount / l)
 85     print "after %d iterations the average error rate is: %f" %(numTests, errorSum/numTests)
 86
 87
 88
 89 """
 90 trainx, trainy = loaddata(‘testSet‘)
 91 print trainy
 92 optimizaion(trainx, trainy)
 93 """
 94
 95 main()
 96
 97 print "cost time: ", (time.time() - st)
 98
 99 """ lineregres
100         # ssi = sigmod(zi) - sigmod(zi) ** 2
101         ss = [sigmodzi - sigmodzi ** 2 for sigmodzi in sigmodz]
102         # errssi = errori * ssi
103         errss = map(lambda x, y: x * y, error, ss)
104         # treri = errssi * trainxi(vector)
105         trer = [errss[i] * array(trainx[i]) for i in xrange(m)]
106         """