Source Code for Module ML.KNN.KNNModel

 1  # $Id: KNNModel.py 2 2006-05-06 22:54:39Z glandrum $ 
 2  # 
 3  #  Copyright (C) 2003 Rational Discovery LLC 
 4  #      All Rights Reserved 
 5  # 
 6   
 7  """ Define the class _KNNModel_, used to represent a k-nearest neighbhors model 
 8   
 9  """ 
10  from ML.KNN import DistFunctions 
11  import bisect 
12 -class KNNModel(object): 
13    """ This is a base class used by KNNClassificationModel 
14    and KNNRegressionModel to represent a k-nearest neighbor predictor. In general 
15    one of this child classes needs to be instantiated. 
16   
17    _KNNModel_s can save the following pieces of internal state, accessible via 
18      standard setter/getter functions - the child object store additional stuff: 
19   
20      1) _Examples_: a list of examples which have been predicted (either classified 
21                      or values predicted) 
22   
23      2) _TrainingExamples_: List of training examples (since this is a KNN model these examples 
24                             along with the value _k_ below define the model) 
25   
26      3) _TestExamples_: the list of examples used to test the model 
27   
28      4) _k_: the number of closest neighbors used for prediction 
29   
30    """ 
31 -  def __init__(self, k, attrs, dfunc) : 
32      self._setup(k, attrs, dfunc) 
33         
34 -  def _setup(self, k, attrs, dfunc) : 
35      self._examples = [] 
36      self._trainingExamples = [] 
37      self._testExamples = [] 
38      self._k = k 
39      self._attrs = attrs 
40      self._dfunc = dfunc 
41      self._name = "" 
42   
43 -  def GetName(self) : 
44      return self_name 
45   
46 -  def SetName(self, name) : 
47      self._name = name 
48   
49 -  def GetExamples(self) : 
50      return self._examples 
51   
52 -  def SetExamples(self, examples): 
53      self._examples = examples 
54   
55 -  def GetTrainingExamples(self): 
56      return self._trainingExamples 
57   
58 -  def SetTrainingExamples(self,examples): 
59      self._trainingExamples = examples 
60   
61 -  def GetTestExamples(self) : 
62      return self._testExamples 
63   
64 -  def SetTestExamples(self, examples) : 
65      self._testExamples = examples 
66   
67 -  def GetNeighbors(self,example): 
68      """ Returns the k nearest neighbors of the example 
69   
70      """ 
71      # we'll maintain a sorted list of nearest neighbors in res: 
72      res = [(1e8,0)]*self._k 
73      for trex in self._trainingExamples: 
74        dist = self._dfunc(trex, example, self._attrs) 
75        knn = (dist, trex) 
76        if dist < res[-1][0]: 
77          loc = bisect.bisect(res,knn) 
78          res.insert(loc,knn) 
79          res.pop() 
80      return res 
81