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     Choosing the correct parameters whether is underfitting or overfitting
    
 
   
   
    
   
   
  
  
   
  
  
   
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     Much harder evaluate hypothesis if we have much more features
    
 
   
   
   
  
   
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     Split training examples, for first the usual training set.
    
 
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     The second, is the test set.
    
 
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     70% for training set and 30% set for test set for the split term
    
 
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     Recommended for the training set to be shuffled, or random sorted
    
 
   
   
   
  
   
  
  
   
  
  
  
   
  
  
   
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     Inject the theta from J theta training set and implement it for theta in Jerror test
    
 
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     These are the test error for linear regression
    
 
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     How about logistic regression at classification?
    
 
   
   
   
  
   
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     The process is similar
    
 
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     Takes theta from 70% examples, that is training set, then plug in the theta for J error
    
 
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     Sometimes there's alternative, that is missclassfication method that simpler
    
 
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     If the hyphothesis is inccorrect predicting the value of output, then label 0 to hyphotesis, 1 otherwise
    
 
   
   
    
   
   
  
   
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     These are few examples for evaluating hyphotesis
    
 
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     Next, Choose what features, or degree of plynomials, or choosing regularization for learning algorithm